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This paper develops a global precipitation rate retrieval algorithm for the Advanced Microwave Sounding Unit (AMSU), which observes 23-191 GHz. The algorithm was trained using a numerical weather prediction (NWP) model (MM5) for 106 globally distributed storms that predicted brightness temperatures consistent with those observed simultaneously by AMSU. Neural networks were trained to retrieve hydrometeor water-paths, peak vertical wind, and 15-mm average surface precipitation rates for rain and snow at 15-km resolution at all viewing angles. Different estimators were trained for land and sea, where surfaces classed as snow or ice were generally excluded from this paper. Surface-sensitive channels were incorporated by using linear combinations [principal components (PCs)] of their brightness temperatures that were observed to be relatively insensitive to the surface, as determined by visual examination of global images of each brightness temperature spectrum PC. This paper also demonstrates that multiple scattering in high microwave albedo clouds may help explain the observed consistency for a global set of 122 storms between AMSU-observed 50-191-GHz brightness temperature distributions and corresponding distributions predicted using a cloud-resolving mesoscale NWP model (MMS) and a two-stream radiative transfer model that models icy hydrometeors as spheres with frequency-dependent densities. The AMSU/MM5 retrieval algorithm developed in Part I of this paper is evaluated in Part II on a separate paper. [ABSTRACT FROM AUTHOR]

Abstract: The hydro-meteorological evaluation of a flood event in July 1997 (the Odra flood in Central Europe) demonstrated that new procedures to estimate design floods for the reservoir outflow structures in the Czech Republic (CR) were needed. Therefore, the techniques of the estimation of Probable Maximum Precipitation (PMP) were developed in a national research project (1998–2000), and the activity focused on the improvement of the area related PMP estimates was going on within a present national project. In the frame of the evaluation of the next extreme precipitation event in August 2002 (the Labe flood in the CR and Germany), we compared the catchments related precipitation with the PMP estimates. In this paper, an outline of the PMP estimation techniques is given and the use of data from the Czech gauges is described, the aim being the statistical derivation of the point and area PMP estimates for precipitation duration of 1 to 5 days. The use of radar data in assessing the maximized area reduction factor is discussed and the relationship resulting from the radar measurements over the CR territory is presented. An evaluation of the radar-based area rainfall enabled us to transform the point PMP to the area PMP estimate designed for the river basins in CR. In the last part of the paper, the results obtained by comparing the rainfalls in 1997 and 2002 flood events with the PMP estimates are presented. The comparison showed that the maximum area rainfalls over small Czech catchments (the 3rd order river basins) did not exceed 63% of the corresponding PMP values. [Copyright &y& Elsevier]

The Eastern Mediterranean region has been exposed to drought episodes, which have been occurring more frequently during the last decades. The objective of the present paper is to study the precipitation regime of the Damascus (Mazzeh) meteoric station by analysing drought characteristics using the Standardized Precipitation Index (SPI) and comparing this with the drought in Cyprus. The cumulative drought conceptis proposed to characterize long-term hydrologic drought, which affects the shallow groundwater productivity in terms of quantity and quality. Gamma probability distribution was fitted to the long-term annual precipitation in Damascus from 1918-1919 to 2007-2008 ( n = 90 years). Generally, a decreasing trend of 17% to the mean annual rainfall of Damascus and 13% to the mean annual rainfall of Cyprus was estimated between 1970 and 2000. The SPI identifies three major extended drought periods: (1) 9 years of severe drought (1954-1963) with an average 20% precipitation deficit per year compared to the mean. (2) 8 years of severe drought (1983-1991) with a 27% deficit per year on average. (3) 9 years of extreme drought (1993-2002) with a 31% deficit per year on average. The cumulative standardized precipitation index (SPI 30) demonstrates positive values for the first period and is indicative of having no effect on the global water balance. SPI 30 exhibits sensitive equilibrium with near zero values / a near zero value (±1.5) for the second period. For the third period, however, the SPI 30 decreases below −10 indicating an extreme hydrological drought that has negative consequences on the recent groundwater recharge. It is required to develop and implement a sustainable groundwater management strategy to reduce long-terms drought risks. Generally, the SPI 30 in Cyprus is parallel to that in Damascus with a 3-5 year delay. Thus, the central zone of the Eastern Mediterranean region is facing big challenges and has been suffering from three decades of moderate to severe hydrological drought (SPI 30=−5 to −10) causing a severe decrease in springs discharges of the region. Therefore, in order to reduce the climate change effects on water resources, it is necessary to adopt a sustainable proactive management plan during the frequent severe droughts. [ABSTRACT FROM AUTHOR]

The upper Sacramento River watershed is vital to California's water supply and is susceptible to major floods. Orographic precipitation in this complex terrain involves both atmospheric rivers (ARs) and the Sierra barrier jet (SBJ). The south-southeasterly SBJ induces orographic precipitation along south-facing slopes in the Mt. Shasta-Trinity Alps, whereas landfalling ARs ascend up and over the statically stable SBJ and induce orographic precipitation along west-facing slopes in the northern Sierra Nevada. This paper explores the occurrence of extreme daily precipitation (EDP) in this region in association with landfalling ARs and the SBJ. The 50 wettest days (i.e., days with EDP) for water years (WYs) 2002-11 based on the average of daily precipitation from eight rain gauges known as the Northern Sierra 8-Station Index (NS8I) are compared to dates from an SSM/I satellite-based landfalling AR-detection method and dates with SBJ events identified from nearby wind profiler data. These 50 days with EDP accounted for 20% of all precipitation during the 10-WY period, or 5 days with EDP per year on average account for one-fifth of WY precipitation. In summary, 46 of 50 (92%) days with EDP are associated with landfalling ARs on either the day before or the day of precipitation, whereas 45 of 50 (90%) days with EDP are associated with SBJ conditions on the day of EDP. Forty-one of 50 (82%) days with EDP are associated with both a landfalling AR and an SBJ. The top 10 days with EDP were all associated with both a landfalling AR and an SBJ. [ABSTRACT FROM AUTHOR]

The rain/no-rain classification for the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) fails to detect rain over coasts, where the microwave footprint encompasses a mixture of radiometrically cold ocean and radiometrically warm land. A static land-ocean-coast mask is used to determine the surface type of each satellite footprint. The coast mask is conservatively wide to account for the largest footprints, preventing use of the more appropriate ocean or land algorithm for coastal regions. The purpose of this paper is to develop a classification whereby the smallest region possible is defined as coast. In this endeavor, two major improvements are applied to the land-ocean-coast classification. First, the surface classification based on microwave footprints of the high frequency actually used in rain detection is employed. Second, the footprint area of the surface classification is established using an effective field-of-view size and scan geometry of the TMI. These improvements are applied to the Global Satellite Mapping of Precipitation TMI algorithm. The classification result is validated using the TRMM precipitation radar. The validation shows that these improvements lead to better rain detection in the coastal region. [ABSTRACT FROM AUTHOR]

The National Oceanic and Atmospheric Administration (NOAA) Geostationary Operational Environmental Satellite series R (GOES-R) will greatly expand the ability to observe the earth from geostationary orbit compared to the current-generation GOES, with more than 3 times as many spectral bands and a 75% reduction in footprint size. These enhanced capabilities are beneficial to rainfall rate estimation since they provide sensitivity to cloud-top properties such as phase and particle size that cannot be achieved using the limited channel selection of current GOES. The GOES-R rainfall rate algorithm, which is an infrared-based algorithm calibrated in real time against passive microwave rain rates, has been previously described in an algorithm theoretical basis document (ATBD); this paper describes modifications since the release of the ATBD, including a correction for evaporation of precipitation in dry regions and improved calibration updates. These improvements have been evaluated using a simplified version applicable to current-generation GOES to take advantage of the high-resolution ground validation data routinely available over the conterminous United States. Correcting for subcloud evaporation using relative humidity from a numerical model reduced false alarm rainfall by half and reduced the overall error by 35% for hourly accumulations validated against the National Centers for Environmental Prediction stage IV radar-gauge field; however, the number of missed events did increase slightly. Reducing the size of the calibration regions and increasing the training data requirements improved the consistency of the retrieved rates in time and space and reduced the overall error by an additional 4%. [ABSTRACT FROM AUTHOR]

Vertically and horizontally inhomogeneous distributions of hydrometeors are often observed in precipitating clouds. The 3-D characteristics can then cause errors in the passive microwave rainfall measurements with the current off-nadir viewing sensors' specifications. This result is due to the fact that the same surface rainfall could be associated with different amounts of hydrometeors depending on the sensors' viewing paths. In this paper, we confirmed that the plane-parallel radiative treatment to the atmosphere leaves a notable deficiency in the microwave radiometric signatures, particularly at the higher frequency channels for different viewing directions when largely inhomogeneous precipitating clouds are accompanied by significant ice particles. The mean differences between the two brightness temperature fields with two opposite azimuthal viewing directions were up to approximately 40 °K for the vertically polarized channel at 85.5 GHz in the case study. The impact of the 3-D effect on the passive microwave rainfall estimations was also examined by synthetic retrievals employing a Bayesian methodology. The results showed that the uncertainty in the rainfall estimations due to the 3-D effect depended on the viewing directions considered in the a priori information. It was also found that taking more viewing angles or the azimuth angles in the a priori information into consideration tended to moderate the retrieval difference that resulted from the different viewing directions. In addition, the retrieval uncertainty related to the 3-D effect appeared to be more significant for heavy rainfall cases with large amounts of ice particles, as expected. [ABSTRACT FROM PUBLISHER]

In this paper we determined the phosphorus (P) concentration in precipitation, and calculated the annual P deposition rate at three study sites located in northern Poland. We observed that the mean annual volume-weighted concentration of mineral phosphorus (Pmin) in wet deposition varies from site to site. The estimated annual wet deposition rate of Pmin in the study region amounted from 0.1 to 0.39 kg/ha. The concentration and deposition rate of Pmin in the southern part of the study region was significantly lower than that in the northern and central part. We detected that the Pmin deposition was strongly positively correlated with the fraction of arable land in the study site vicinity, and also positively correlated with the mineral P fertilizer consumption in the area. The mean annual volume-weighted concentration of Pmin in wet deposition varied from 0.015 mg/l in the area of the lowest arable land percentage and the lowest mineral fertilizer consumption, to 0.046 mg/l in the area where the arable lands comprise 84% of agricultural land, and mineral P fertilizer consumption exceeded 33 kg/ha. In the P soil surface balance the atmospheric wet deposition represents 2.1-5.6% of annual total inputs of total P. The level of atmospheric P input varies widely by catchment and is related to land use (fertilizing, intensity and type of crop production). [ABSTRACT FROM AUTHOR]

This paper assesses the influence of radiative forcing and latent heating on the development and maintenance of cloud-top generating cells (GCs) in high-resolution idealized Weather Research and Forecasting Model simulations with initial conditions representative of the vertical structure of a cyclone observed during the Profiling of Winter Storms campaign. Simulated GC kinematics, structure, and ice mass are shown to compare well quantitatively with Wyoming Cloud Radar, cloud probe, and other observations. Sensitivity to radiative forcing was assessed in simulations with longwave-only (nighttime), longwave-and-shortwave (daytime), and no-radiation parameterizations. The domain-averaged longwave cooling rate exceeded 0.50 K h−1 near cloud top, with maxima greater than 2.00 K h−1 atop GCs. Shortwave warming was weaker by comparison, with domain-averaged values of 0.10-0.20 K h−1 and maxima of 0.50 K h−1 atop GCs. The stabilizing influence of cloud-top shortwave warming was evident in the daytime simulation's vertical velocity spectrum, with 1% of the updrafts in the 6.0-8.0-km layer exceeding 1.20 m s−1, compared to 1.80 m s−1 for the nighttime simulation. GCs regenerate in simulations with radiative forcing after the initial instability is released but do not persist when radiation is not parameterized, demonstrating that radiative forcing is critical to GC maintenance under the thermodynamic and vertical wind shear conditions in this cyclone. GCs are characterized by high ice supersaturation (RHice > 150%) and latent heating rates frequently in excess of 2.00 K h−1 collocated with vertical velocity maxima. Ice precipitation mixing ratio maxima of greater than 0.15 g kg−1 were common within GCs in the daytime and nighttime simulations. [ABSTRACT FROM AUTHOR]

This paper demonstrates the impact of the enhancement in detectability by the dual-frequency precipitation radar (DPR) on board the Global Precipitation Measurement (GPM) core observatory. By setting two minimum detectable reflectivities-12 and 18 dB Z-artificially to 6 months of GPM DPR measurements, the precipitation occurrence and volume increase by ~21.1% and ~1.9%, respectively, between 40°S and 40°N. GPM DPR is found to be able to detect light precipitation, which mainly consists of two distinct types. One type is shallow precipitation, which is most significant for convective precipitation over eastern parts of subtropical oceans, where deep convection is typically suppressed. The other type is probably associated with lower parts of anvil clouds associated with organized precipitation systems. While these echoes have lower reflectivities than the official value of the minimum detectable reflectivity, they are found to mostly consist of true precipitation signals, suggesting that the official value may be too conservative for some sort of meteorological analyses. These results are expected to further the understanding of both global energy and water budgets and the diabatic heating distribution. [ABSTRACT FROM AUTHOR]

Using satellite measurements in microwave bands to retrieve precipitation over land requires proper discrimination of the weak rainfall signals from strong and highly variable background Earth surface emissions. Traditionally, land retrieval methods rely on a weak signal of rainfall scattering on high-frequency channels and make use of empirical thresholding and regression-based techniques. Because of the increased surface signal interference, retrievals over radiometrically complex land surfaces-snow-covered lands, deserts, and coastal areas-are particularly challenging for this class of retrieval techniques. This paper evaluates the results by the recently proposed Shrunken Locally Linear Embedding Algorithm for Retrieval of Precipitation (ShARP) using data from the Tropical Rainfall Measuring Mission (TRMM) satellite. The study focuses on a radiometrically complex region, partly covering the Tibetan highlands, Himalayas, and Ganges-Brahmaputra-Meghna River basins, which is unique in terms of its diverse land surface radiation regime and precipitation type, within the TRMM domain. Promising results are presented using ShARP over snow-covered land surfaces and in the vicinity of coastlines, in comparison with the land rainfall retrievals of the standard TRMM 2A12, version 7, product. The results show that ShARP can significantly reduce the rainfall overestimation due to the background snow contamination and markedly improve detection and retrieval of rainfall in the vicinity of coastlines. During the calendar year 2013, compared to TRMM 2A25, it is demonstrated that over the study domain the root-mean-square difference can be reduced up to 38% annually, while the improvement can reach up to 70% during the cold months of the year. [ABSTRACT FROM AUTHOR]

A measurement scheme aimed at investigating precipitation properties based on collocated disdrometer and profiling instruments is used in many experimental campaigns. Raindrop size distribution (RSD) estimated by disdrometer is referred to the ground level; the collocated profiling instrument is supposed to provide complementary estimation at different heights of the precipitation column above the instruments. As part of the Special Observation Period 1 of the HyMeX (Hydrological Cycle in the Mediterranean Experiment) project, conducted between 5 September and 6 November 2012, a K-band vertically pointing micro rain radar (MRR) and a 2D video disdrometer (2DVD) were installed close to each other at a site in the historic center of Rome (Italy). The raindrop size distributions collected by 2D video disdrometer are considered to be fairly accurate within the typical sizes of drops. Vertical profiles of raindrop sizes up to 1085 m are estimated from the Doppler spectra measured by the micro rain radar with a height resolution of 35 m. Several issues related to vertical winds, attenuation correction, Doppler spectra aliasing, and range-Doppler ambiguity limit the performance of MRR in heavy precipitation or in convection, conditions that frequently occur in late summer or in autumn in Mediterranean regions. In this paper, MRR Doppler spectra are reprocessed, exploiting the 2DVD measurements at ground to estimate the effects of vertical winds at 105 m (the most reliable MRR lower height), in order to provide a better estimation of vertical profiles of raindrop size distribution from MRR spectra. Results show that the reprocessing procedure leads to a better agreement between the reflectivity computed at 105 m from the reprocessed MRR spectra and that obtained from the 2DVD data. Finally, vertical profiles of MRR-estimated RSDs and their relevant moments (namely median volume diameter and reflectivity) are presented and discussed in order to investigate the microstructure of rain both in stratiform and convective conditions. [ABSTRACT FROM AUTHOR]

The assessment of future precipitation variations prevailing in an area is essential for the research regarding climate and climate change. The current paper focuses on 3 selected areas in Greece that present different climatic characteristics due to their location and aims to assess and compare the future variation of annual and seasonal precipitation. Future precipitation data from the ENSEMBLES anthropogenic climate-change (ACC) global simulations and the Climate version of the Local Model (CLM) were obtained and analyzed. The climate simulations were performed for the future periods 2021–2050 and 2071–2100 under the A1B and B1 scenarios. Mann–Kendall test was applied to investigate possible trends. Spatial distribution of precipitation was performed using a combination of dynamic and statistical downscaling techniques and Kriging method within ArcGIS 10.2.1. The results indicated that for both scenarios, reference periods and study areas, precipitation is expected to be critically decreased. Additionally, Mann–Kendall test application showed a strong downward trend for every study area. Furthermore, the decrease in precipitation for the Ardas River basin characterized by the continental climate will be tempered, while in the Sperchios River basin it will be smoother due to the influence of some minor climatic variations in the basins' springs in the highlands where milder conditions occur. Precipitation decrease in the Geropotamos River basin which is characterized by Mediterranean climate will be more vigorous. B1 scenario appeared more optimistic for the Ardas and Sperchios River basins, while in the Geropotamos River basin, both applied scenarios brought similar results, in terms of future precipitation response. [ABSTRACT FROM AUTHOR]

Statistical downscaling (SD) methods have become a popular, low-cost and accessible means of bridging the gap between the coarse spatial resolution at which climate models output climate scenarios and the finer spatial scale at which impact modellers require these scenarios, with various different SD techniques used for a wide range of applications across the world. This paper compares the Generator for Point Climate Change (GPCC) model and the Statistical DownScaling Model (SDSM)-two contrasting SD methods-in terms of their ability to generate precipitation series under non-stationary conditions across ten contrasting global climates. The mean, maximum and a selection of distribution statistics as well as the cumulative frequencies of dry and wet spells for four different temporal resolutions were compared between the models and the observed series for a validation period. Results indicate that both methods can generate daily precipitation series that generally closely mirror observed series for a wide range of non-stationary climates. However, GPCC tends to overestimate higher precipitation amounts, whilst SDSM tends to underestimate these. This infers that GPCC is more likely to overestimate the effects of precipitation on a given impact sector, whilst SDSM is likely to underestimate the effects. GPCC performs better than SDSM in reproducing wet and dry day frequency, which is a key advantage for many impact sectors. Overall, the mixed performance of the two methods illustrates the importance of users performing a thorough validation in order to determine the influence of simulated precipitation on their chosen impact sector. [ABSTRACT FROM AUTHOR]

This paper analyzes climatological characteristics and temporal variation of the start and end dates of the rainy season over East Asia using a daily precipitation dataset for the time period 1951-2009. The rainy season is defined by a 5-day rainfall standard, and the regional average time series is constructed by applying the weighted-average method. Results show that the rainy season starts later, ends earlier and lasts shorter from southeast to northwest. In spring, the rainy belt slowly moves northward from 30 to 33°N in China and from 33 to 36°N on the Korean Peninsula and Japanese Islands. From 1951 to 2009, the rainy season generally began earlier in China but later in Korea and Japan, and it ended earlier at latitudes north of 35°N and later south of 35°N. The region-averaged start and end dates of the rainy season in the study region insignificantly advanced, and the duration of the rainy season insignificantly increased from 1951 to 2009. The rainy season duration slightly decreased in the Russian Far East and in northern and western China, and significantly decreased on the Korean Peninsula and the southern Hokkaido Islands, though it obviously increased in the Yangtze--Huaihe River Basins. [ABSTRACT FROM AUTHOR]

Assimilation of satellite precipitation data into numerical models presents several difficulties, with two of the most important being the non-Gaussian error distributions associated with precipitation, and large model and observation errors. As a result, improving the model forecast beyond a few hours by assimilating precipitation has been found to be difficult. To identify the challenges and propose practical solutions to assimilation of precipitation, statistics are calculated for global precipitation in a low-resolution NCEP Global Forecast System (GFS) model and the TRMM Multisatellite Precipitation Analysis (TMPA). The samples are constructed using the same model with the same forecast period, observation variables, and resolution as in the follow-on GFS/TMPA precipitation assimilation experiments presented in the companion paper. The statistical results indicate that the T62 and T126 GFS models generally have positive bias in precipitation compared to the TMPA observations, and that the simulation of the marine stratocumulus precipitation is not realistic in the T62 GFS model. It is necessary to apply to precipitation either the commonly used logarithm transformation or the newly proposed Gaussian transformation to obtain a better relationship between the model and observational precipitation. When the Gaussian transformations are separately applied to the model and observational precipitation, they serve as a bias correction that corrects the amplitude-dependent biases. In addition, using a spatially and/or temporally averaged precipitation variable, such as the 6-h accumulated precipitation, should be advantageous for precipitation assimilation. [ABSTRACT FROM AUTHOR]

This paper focuses on analysis of the time series of 7 Be and 210 Pb activity measured in moss, and the amount, as well as duration of precipitation, to gain a better understanding of the possible relationships between airborne radionuclide deposition and precipitation. Here we consider whether the amount of these airborne radionuclides in moss samples is a cumulative measure of radionuclide deposition and decay, and a new approach for analyses of the relationships between precipitation and moss activity concentrations is suggested. Through these analyses it was shown that comparison of cumulative activity measured at one location using moss, normalized by values of cumulative amount or duration of precipitation, showed different regimes of airborne radionuclide deposition. [ABSTRACT FROM AUTHOR]

The High-Altitude Imaging Wind and Rain Airborne Profiler (HIWRAP) is a dual-frequency (Ka- and Ku-bands), dual-beam (30° and 40° incidence angles), and conical scanning Doppler radar designed for operation on the NASA high-altitude (∼19 km) Global Hawk Unmanned Aerial System. HIWRAP was developed under the support of the NASA Instrument Incubator Program for studies of tropical storms and severe weather events. It utilizes solid-state transmitters along with a novel transmit and receive waveform scheme that results in a system with compact size, light weight, less power consumption, and lower cost compared to radars currently in use for precipitation and Doppler wind measurements. By combining volume backscattering measurements at Ku- and Ka-bands, HIWRAP is capable of imaging radar reflectivity and 3-D wind fields in clouds and precipitation. In addition, HIWRAP is also capable of measuring surface winds in an approach similar to SeaWinds on QuikSCAT. HIWRAP operating frequencies are similar to those used by the NASA Global Precipitation Measurement (GPM) Dual-frequency Precipitation Radar, making it suitable for providing airborne validation data for the GPM mission. This paper describes the scientific motivation for the development of HIWRAP as well as the system hardware, aircraft integration, and recent flight activities. Data from recent science flights are also presented. [ABSTRACT FROM AUTHOR]

This paper clarifies that the skillful time-scale characteristic of a model is one of the key factors to reproduce the amount precipitation at a specific location with the model. A comparison with data from an operational weather station of the Japan Meteorological Agency in Tokyo (Ote-machi) revealed that a model needed That a model requires 5-km-grid resolution and below to represent the power spectrum of hourly precipitation. A model with a higher resolution is probably needed to simulate hourly precipitation in Tokyo during the summer monsoon season. [ABSTRACT FROM AUTHOR]

The estimation of precipitation across the globe from satellite sensors provides a key resource in the observation and understanding of our climate system. Estimates from all pertinent satellite observations are critical in providing the necessary temporal sampling. However, consistency in these estimates from instruments with different frequencies and resolutions is critical. This paper details the physically based retrieval scheme to estimate precipitation from cross-track (XT) passive microwave (PM) sensors on board the constellation satellites of the Global Precipitation Measurement (GPM) mission. Here the Goddard profiling algorithm (GPROF), a physically based Bayesian scheme developed for conically scanning (CS) sensors, is adapted for use with XT PM sensors. The present XT GPROF scheme utilizes a model-generated database to overcome issues encountered with an observational database as used by the CS scheme. The model database ensures greater consistency across meteorological regimes and surface types by providing a more comprehensive set of precipitation profiles. The database is corrected for bias against the CS database to ensure consistency in the final product. Statistical comparisons over western Europe and the United States show that the XT GPROF estimates are comparable with those from the CS scheme. Indeed, the XT estimates have higher correlations against surface radar data, while maintaining similar root-mean-square errors. Latitudinal profiles of precipitation show the XT estimates are generally comparable with the CS estimates, although in the southern midlatitudes the peak precipitation is shifted equatorward while over the Arctic large differences are seen between the XT and the CS retrievals. [ABSTRACT FROM AUTHOR]

A young Mars may well have possessed a global dipolar magnetic field that provided protection for the planet׳s atmosphere from the space weather environment. Against this background, we study in the present paper the effect of various dipole magnetic fields on particle precipitation (range 10 keV–4.5 MeV) on the upper Martian atmosphere as the magnetosphere gradually declined to become an induced magnetosphere. We utilized a hybrid plasma model to provide, in a self-consistent fashion, simulations (that included ion-kinetic effects) of the interaction between the Martian obstacle (magnetized or otherwise) and the solar wind. Besides the intrinsic dipole, with field strengths of ~100 nT and below, we assume modern solar and atmospheric parameters to examine the effect of the single variable, that is the dipole strength. We thereby investigated the precipitation of solar energetic particles on the upper atmosphere of the planet in circumstances characterized by the evolution of a diminishing Martian dynamo that initially generated an ideal dipolar field. It is demonstrated that an assumed Martian dipole would have provided, in the energy range investigated, significant shielding against proton impingement and that the interaction between the solar wind and the assumed Martian magnetic dipole would have been responsible for generating the shielding effect identified. [ABSTRACT FROM AUTHOR]

Climate regionalization is an important but often under-emphasized step in studies of climate variability. While most investigations of regional climate make at least an implicit attempt to focus on a study region or sub-regions that are climatically coherent in some respect, rigorous climate regionalization--in which the study area is divided on the basis of the most relevant climate metrics and at a resolution most appropriate to the data and the scientific question--has the potential to enhance the precision and explanatory power of climate studies in many cases. To facilitate the application of rigorous regionalization for climate studies, we introduce an improved hierarchical clustering method, describe a new open-source R package designed specifically for climate regionalization, and offer concise suggestions for performing appropriate regionalization. This paper describes the regionalization algorithms and presents a demonstration application in which the R package is used to regionalize Africa on the basis of interannual precipitation variability. Both the proposed methodology and the R package can be used for a broad range of applications and over different areas of the globe. [ABSTRACT FROM AUTHOR]

The Goddard profiling algorithm has evolved from a pseudoparametric algorithm used in the current TRMM operational product (GPROF 2010) to a fully parametric approach used operationally in the GPM era (GPROF 2014). The fully parametric approach uses a Bayesian inversion for all surface types. The algorithm thus abandons rainfall screening procedures and instead uses the full brightness temperature vector to obtain the most likely precipitation state. This paper offers a complete description of the GPROF 2010 and GPROF 2014 algorithms and assesses the sensitivity of the algorithm to assumptions related to channel uncertainty as well as ancillary data. Uncertainties in precipitation are generally less than 1%-2% for realistic assumptions in channel uncertainties. Consistency among different radiometers is extremely good over oceans. Consistency over land is also good if the diurnal cycle is accounted for by sampling GMI product only at the time of day that different sensors operate. While accounting for only a modest amount of the total precipitation, snow-covered surfaces exhibit differences of up to 25% between sensors traceable to the availability of high-frequency (166 and 183 GHz) channels. In general, comparisons against early versions of GPM's Ku-band radar precipitation estimates are fairly consistent but absolute differences will be more carefully evaluated once GPROF 2014 is upgraded to use the full GPM-combined radar-radiometer product for its a priori database. The combined algorithm represents a physically constructed database that is consistent with both the GPM radars and the GMI observations, and thus it is the ideal basis for a Bayesian approach that can be extended to an arbitrary passive microwave sensor. [ABSTRACT FROM AUTHOR]

This paper is dealing with the assessment of climate change scenarios on selected meteorological variables at the Lake Karla watershed, central Greece and it is a contribution to the "HYDROMENTOR" research project. A statistical downscaling method has been employed to estimate monthly precipitation and temperature time series for future climate periods. The outputs of the Canadian Centre for Climate Modeling Analysis Global Circulation Model CGCM3 were applied for three socioeconomic scenarios, namely SRES B 1, SRES A 1B and SRES A2 for the assessment of climate change impact on precipitation and temperature. The methodology has been developed for the historical period 1980-2000 and applied for two future periods 2030-2050 and 2080-2100. Historical and future periods were compared for monthly and annual basis using various statistical criteria such as the mean and standard deviation. Results showed that climate change will have minor impacts on precipitation and even smaller impacts on temperature. [ABSTRACT FROM AUTHOR]

ABSTRACT In this paper, a 10-year daily accumulated precipitation analysis of Madeira highland is presented, as well as the relationship between meridional water vapour transport during 10 winter seasons and the precipitation recorded in the island during the same period. Here, the meridional water vapour transport is considered as occurring in narrow corridors known as atmospheric rivers - ARs - which were visually identified in the total precipitable water vapour field extracted from Atmospheric Infrared Sounder ( AIRS) data within a domain covering the North Atlantic Ocean. European Centre for Medium-range Weather Forecasts ( ECMWF) analysis was also used when necessary. Daily precipitation during the period covered by the study evidenced generally dry summers, whereas the highest values for daily accumulated precipitation were recorded mainly during the winter and also during the autumn and spring. Image analysis shows that moist air originating mainly in the Caribbean Sea flows northward or eastward, intersecting, on some occasions, the island during the winter season, often during a stage of dissipation. The orientation of the flow and the amount of water vapour transported to the island are important features, contributing to the occurrence of significant precipitation events. In fact, the moist environment created by ARs may favour the occurrence of precipitation, but this is not the sole factor favouring high rainfall over Madeira. [ABSTRACT FROM AUTHOR]

To elaborate a complete model of the Earth system, it is necessary to include the model of dynamics of Greenland and Antarctic ice sheets into the General Circulation Model (GCM). The problem is that spatial and temporal scales of ice sheet dynamics, on one hand, and the dynamics of atmosphere and the ocean, on the other hand, differ considerably. In order to unite them in one model, implementation of one or another downscaling procedure is required. For this purpose we elaborated an energy- and water balance model of the Greenland ice sheet (EWBM-G) serving as a buffer between the GCM INMCM and the ice sheet model. EWBM-G describes heat and water vapor diffusion in a limited domain with the boundary conditions transferred from the INMCM. This paper describes the model and set-up of the numerical experiments aiming at calculation surface air temperature and annual precipi-tation amount in Greenland in accordance with the simulated pre-industrial climate. The results of calculations are compared with observations and reconstructions. [ABSTRACT FROM AUTHOR]

The decomposition sequence of the supersaturated solid solution leading to the formation of the equilibrium S (Al 2 CuMg) phase in Al Cu Mg alloys has long been the subject of ambiguity and debate. Recent high-resolution synchrotron powder diffraction experiments have shown that the decomposition sequence does involve a metastable variant of the S phase (denoted S1), which has lattice parameters that are distinctly different to those of the equilibrium S phase (denoted S2). In this paper, the difference between these two phases is resolved using high-resolution synchrotron and neutron powder diffraction and atom probe tomography, and the transformation from S1 to S2 is characterised in detail by in situ synchrotron powder diffraction. The results of these experiments confirm that there are no significant differences between the crystal structures of S1 and S2, however, the powder diffraction and atom probe measurements both indicate that the S1 phase forms with a slight deficiency in Cu. The in situ isothermal aging experiments show that S1 forms rapidly, reaching its maximum concentration in only a few minutes at high temperatures, while complete conversion to the S2 phase can take thousands of hours at low temperature. The kinetics of S phase precipitation have been quantitatively analysed for the first time and it is shown that S1 phase forms with an average activation energy of 75 kJ/mol, which is much lower than the activation energy for Cu and Mg diffusion in an Al matrix (136 kJ/mol and 131 kJ/mol, respectively). The mechanism of the replacement of S1 with the equilibrium S2 phase is discussed. [ABSTRACT FROM AUTHOR]

Systematic high quality oceanic in-situ precipitation measurements are requested on an international science level and are essential for improved understanding and validation of hydrological processes in satellite, re-analysis and model data. OceanRAIN, the shipboard “Ocean Rainfall And Ice-phase precipitation measurement Network” for surface validation is, to date, the only systematic long-term disdrometer-based oceanic shipboard precipitation data collection effort to establish a comprehensive statistical basis of precipitation for all climate related hotspots over the global oceans. OceanRAIN utilizes automated disdrometer systems (ODM470) capable of measuring precipitation occurrence, intensity and accumulation and discriminates for rain, snow and mixed-phase precipitation through minute-based particle size distributions. The ODM470 was especially designed for shipboard operation under high and frequently varying wind speeds and rough sea states. This paper provides an overview on the OceanRAIN project, the instrumentation, algorithms, methodology, and data products. The procedure of the data processing chain is outlined, including calibration, shipboard operation, data ingest and quality control. The selected research ships do not circumvent high impact weather, allowing for a collection of the full precipitation spectrum including extremes. By October 2014 the fast growing OceanRAIN database comprised more than 3.7 million minutes of precipitation measurements (including true zeros) since its start in 2010. OceanRAIN aims at increasing knowledge about oceanic precipitation, improving error characterization of GPM (Global Precipitation Measurement) era precipitation retrievals, adding to the continual improvement of the satellite retrieval algorithms, as well as benchmarking existing satellite-based climatologies, re-analysis and model data. The accumulating data volume can be utilized for statistical and process study applications on different temporal and spatial scales, microphysical studies of rain and snow formation, and yields insight to the point-to-area problem of precipitation. Information on OceanRAIN including data products is available via http://www.oceanrain.org . [ABSTRACT FROM AUTHOR]

This paper examines differences between Version 6 (V6) and Version 7 (V7) 3-hourly TRMM (Tropical Rainfall Measuring Mission) Multi-Satellite Precipitation Analysis (TMPA 3B42) research products in JJA (June, July and August) and DJF (December, January and February) over a 13-year period from 1998 to 2010 on a global scale. Different surface types and rain regimes are considered in the comparison. The study finds that more rain events are found in V7 than those in V6 in both JJA and DJF, especially over oceans. Overall, both versions show a good agreement in moderate and heavy rain regimes. High Pearson’s correlation coefficients are found in tropical rain band regions. Histograms of both versions are very similar; however higher frequencies of rain events are found in V7 in light rain regime, especially over oceans, than those in V6. For light rain, rainfall estimates in V6 are less than those in V7 over land and oceans in both seasons. For moderate rain, rainfall estimates in V6 are larger than those in V7 over land in most years. Over oceans, it is a mixed situation in which V6 > V7 for some years and V6 < V7 for the other years. For heavy rain, rainfall estimates in V6 are larger than those in V7 throughout all JJA and DJF seasons for both land and oceans, which is also shown in a case study. Large variance in the individual differences is found in light rain and less in heavy rain. No apparent trends are observed. For light rain, all statistics support that there is an uncertainty issue in both versions. [ABSTRACT FROM AUTHOR]

Future projection of air temperature and precipitation due to climate change plays an important role in shaping the water resources management plans in arid and semi-arid countries such as the United Arab Emirates (UAE). The effect of local topography, land use, and sealand contrasts are generally dwarfed in the coarse global circulation models [ocean atmosphere global climate models (OAGCMs)] results. Statistical downscaling (SD) is a statistical tool relating OAGCM outputs (predictors) to finer local observed weather data (predictands) to improve future predictions. SD is used in this study to downscale the Hadley Model (HadCM3) predictors using local observations at two stations representing the dominating bioclimatic zones in the UAE. The paper proposes a rigorous and systematic methodology to guide the selection of dominant predictors in the projection scenarios. The proposed methodology is applied for the UAE but can be easily adopted for any other area. The calibrated model, used to project future scenarios in the region, revealed a range of increase of the annual mean maximum temperature of 2.79-3.80°C and a range of reduction of annual precipitation of 16.80-37.00% by 2080 at the considered stations. Impacts of climate change on the UAE's water resources management are discussed in light of the downscaled estimates for temperature and precipitation. Because a major portion of the water resources is devoted to agriculture, temperature impacts are quite significant. However, the impacts of precipitation are hardly detectable at the national scale. Instead, the impacts of reduced precipitation will be of more localized significance in mountainous regions that are critically dependent on precipitation for water resources. [ABSTRACT FROM AUTHOR]

The start and duration of a drought are often not easy to define. The advance and onset are usually slow and the social and economic impacts can then extend over a long period. In this study, the Standardized Precipitation Index (SPI) was used to describe and compare droughts in different periods and regions under different climatic conditions. The importance of the index lies in its simplicity and in its ability to identify the beginning and end of a drought event. Thus it may be a useful tool for drought contingency planning. This paper examines the SPI by evaluating its application using historical precipitation data from nine weather stations in China. Different time series data covering the period 1980 to 2011 and for differing timescales of 3, 9 and 24 months were used. The results underline the potential of the SPI to inform drought alerts and forecasting efforts as part of a drought contingency planning strategy. [ABSTRACT FROM AUTHOR]

The Andes Cordillera plays a role in driving moisture and heat from tropical onto subtropical South America. It forces the development of a lee-side trough that covers most of western Argentina and a low-level jet that maximizes over Paraguay, eastern Bolivia and northern Argentina and is tightly linked to precipitation variability over much of central and southeastern South America. Its steep slopes and the large zonal gradients in topography between the Equator and 40°S are misrepresented in climate simulations using Global Climate Models (GCM) with resolutions coarser than about 100 km, since they naturally have a poor representation of the Andes and related circulation features. This paper analyses the impact of varying artificially the altitude of the Andes Cordillera in a GCM as well as increasing the horizontal resolution to study how these variations determine moisture fluxes and precipitation over selected regions of South America. Results show that the height of the Andes is crucial in shaping moisture fluxes pathways onto subtropical South America all year long. In particular, the low-level jet is only simulated when the Andes heights are doubled. At the same time, the relationship between the Andes shape and the location of the Bolivian High in summer is also discussed. In terms of precipitation, the lowest bias in the simulations is achieved when the horizontal resolution is increased, while in particular near the Andes foothills the simulated annual rainfall is largely determined by the Mountains shape. [ABSTRACT FROM AUTHOR]

Recent studies have used numerical models to estimate the collection efficiency of solid precipitation gauges when exposed to the wind in both shielded and unshielded configurations. The models used computational fluid dynamics (CFD) simulations of the airflow pattern generated by the aerodynamic response to the gauge-shield geometry. These are used as initial conditions to perform Lagrangian tracking of solid precipitation particles. Validation of the results against field observations yielded similarities in the overall behavior, but the model output only approximately reproduced the dependence of the experimental collection efficiency on wind speed. This paper presents an improved snowflake trajectory modeling scheme due to the inclusion of a dynamically determined drag coefficient. The drag coefficient was estimated using the local Reynolds number as derived from CFD simulations within a time-independent Reynolds-averaged Navier-Stokes approach. The proposed dynamic model greatly improves the consistency of results with the field observations recently obtained at the Marshall Field winter precipitation test bed in Boulder, Colorado. [ABSTRACT FROM AUTHOR]

Ensemble-based data assimilation techniques are often applied to land surface models in order to estimate components of terrestrial water and energy balance. Precipitation forcing uncertainty is the principal source of spread among the ensembles that is required for utilizing information in observations to correct model priors. Precipitation fields may have both position and magnitude errors. However, current uncertainty characterizations of precipitation forcing in land data assimilation systems often do no more than applying multiplicative errors to precipitation fields. In this paper, an ensemble-based Bayesian method for characterization of uncertainties associated with precipitation retrievals from spaceborne instruments is introduced. This method is used to produce stochastic replicates of precipitation fields that are conditioned on precipitation observations. Unlike previous studies, the error likelihood is derived using an archive of historical measurements. The ensemble replicates are generated using a stochastic method, and they are intermittent in space and time. The replicates are first projected in a low-dimension subspace using a problem-specific set of attributes. The attributes are derived using a dimensionality reduction scheme that takes advantage of singular value decomposition. A nonparametric importance sampling technique is formulated in terms of the attribute vectors to solve the Bayesian sampling problem. Examples are presented using retrievals from operational passive microwave instruments, and performance of the method is assessed using ground validation measurements from a surface weather radar network. Results indicate that this ensemble characterization approach provides a useful description of precipitation uncertainties with a posterior ensemble that is narrower in distribution than its prior while containing both precipitation position and magnitude errors. [ABSTRACT FROM AUTHOR]

A compact analytical expression of the Fraction Skill Score (FSS) is derived for a case with a single displaced rainband in a rectangular domain. The rainband is oriented parallel to the border and displaced perpendicularly to its orientation. An analytical solution is used to determine some of the properties of the FSS which might also be applicable in other cases. The solution is independent of the length of the rainband (it is valid also for a displaced rainy grid point). The position of the borders perpendicular to the rainband orientation does not influence the FSS value. The position of the other two borders does however influence the FSS value in a complex way; moving a border closer to the rainbands can either increase or decrease the FSS value depending on the location of the borders. FSS is shown to be a monotonically increasing function of the neighbourhood size (regardless of the position of the borders). If the FSS value for a displacement that is half the neighbourhood size is used to define a 'useful' FSS value then the usefulness criterion is somewhat different than presented in the original FSS paper (there is no dependence on the frequency of the observations/forecasts). 'Useful' FSS values are always >1/2 but depend on the position of the borders and the size of the displacement. [ABSTRACT FROM AUTHOR]

Long-term global gridded datasets of observed precipitation are essential for the analysis of the global water and energy cycle, its variability, and possible changes. Several institutions provide those datasets. In 2005 the Global Precipitation Climatology Centre (GPCC) published the so-called Variability Analysis of Surface Climate Observations (VASClimO) dataset. This dataset is especially designed for the investigation of temporal change and variability. To date, however, the GPCC has not published how this dataset has been produced. This paper aims to fill this gap. It provides detailed information on how stations are selected and how data are quality controlled and interpolated. The dataset is based only on station records covering at least 90% of the period 1951-2000. The time series of 9343 stations were used. However, these stations are distributed very inhomogeneously around the globe; 4094 of these stations are within Germany and France. The VASClimO dataset is interpolated from relative deviations of observed monthly precipitation, leading to considerably lower interpolation errors than direct interpolation or the interpolation of absolute deviations. The retransformation from interpolated relative deviations to precipitation is done with local long-term averages of precipitation interpolated from data of the Food and Agriculture Organization of the United Nations. The VASClimO dataset has been interpolated with a method that is based on local station correlations (LSC) that is introduced here. It is compared with ordinary kriging and three versions of Shepard's method. LSC outperforms these methods, especially with respect to the spatial maxima of interpolation errors. [ABSTRACT FROM AUTHOR]

This paper examines the synoptic control of precipitation contrasts across the Cascade Mountains of Washington State during the cool season. The average hourly precipitation for three stations on the western and eastern sides of the barrier is calculated, and composite synoptic conditions are determined for situations when precipitation is greater over the eastern slopes, similar precipitation falls on both sides, moderately greater precipitation falls on the western side, and substantially greater precipitation falls on the western side. Conditions prior to occluded/warm frontal passage are favorable for relatively equal precipitation amounts on both sides of the barrier, with extensive warm advection precipitation spreading over the region. Low-level winds are generally southerly during this period, resulting in less orographic modulation of precipitation on the north-south-oriented Cascades. In contrast, postfrontal conditions are associated with westerly flow, enhanced windward precipitation, and greater drying on the leeward (eastern) slopes. Postfrontal conditions also bring drying aloft and reduced stability at low levels, both of which contribute to the enhancement of precipitation on the western slopes. The variation of the cross-mountain precipitation ratio between El Niño and La Niña years can be explained by the associated synoptic configurations. El Niño years have weaker zonal winds and thus less orographic modulation. Furthermore, the lesser vertical stability of La Niña years enhances precipitation on the windward side of the barrier where shallow convection is released. [ABSTRACT FROM AUTHOR]

The South Asian monsoon is critically important for agricultural production in the region that includes the vast, fertile Indus and Ganges basins. However, the behavior of the South Asian monsoon is not well understood because of its complex nature, and existing instrumental climate records are insufficient for investigating the risks of the low-frequency but high-impact megadroughts that have historically occurred. This paper develops an inverse Palmer drought severity index (PDSI) model to retrieve paleoprecipitation for the region during the time period of 1300-1899, using available data of the water-holding capacity of soil, temperature, and reconstructed PDSI based on the tree-ring analysis of Cook et al.. Temperature data are reconstructed by a regression analysis utilizing an existing temperature reconstruction in an adjacent region and the Pacific decadal oscillation. Based on the retrieved paleoprecipitation, several megadroughts are identified during the reconstruction period. The drought frequency in the Indus basin is higher than that in the Ganges basin. The intensity, frequency, and spatial extent of severe droughts increased from 1300-1899 to 1900-2010. As a signal of climate change, increasing intensity and frequency of severe drought in the Indus and Ganges River basins needs adaptation strategies and drought preparedness measures to secure the food production in this area. [ABSTRACT FROM AUTHOR]

Although atmospheric rivers (ARs) typically weaken following landfall, those that penetrate inland can contribute to heavy precipitation and high-impact weather within the interior of western North America. In this paper, the authors examine the evolution of ARs over western North America using trajectories released at 950 and 700 hPa within cool-season ARs along the Pacific coast. These trajectories are classified as coastal decaying, inland penetrating, or interior penetrating based on whether they remain within an AR upon reaching selected transects over western North America. Interior-penetrating AR trajectories most frequently make landfall along the Oregon coast, but the greatest fraction of landfalling AR trajectories that eventually penetrate into the interior within an AR is found along the Baja Peninsula. In contrast, interior-penetrating AR trajectories rarely traverse the southern 'high' Sierra. At landfall, interior-penetrating AR trajectories are associated with a more amplified flow pattern, more southwesterly (vs westerly) flow along the Pacific coast, and larger water vapor transport ( qυ). The larger initial qυ of interior-penetrating AR trajectories is due primarily to larger initial water vapor q and wind speed υ for those initiated at 950 and 700 hPa, respectively. Inland- and interior-penetrating AR trajectories maintain large qυ over the interior partially due to increases in υ that offset decreases in q, particularly in the vicinity of topographical barriers. Therefore, synoptic conditions and trajectory pathways favoring larger initial qυ at the coast, limited water vapor depletion by orographic precipitation, and increases in υ over the interior are keys to differentiating interior-penetrating from coastal-decaying ARs. [ABSTRACT FROM AUTHOR]

The Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) measures reflectivity downward from space and provides observations of the vertical distributions of precipitation over land as well as the ocean. It overpasses the southern part of the Korean Peninsula where (i) a dense network of operational S-band scanning radars is available and (ii) various types of precipitation occur. By utilizing a 3D reflectivity composite from the ground S-band radar (GR) observations, this paper shows a comparison of reflectivity profiles observed with both PR and GR focusing on their vertical structure. For four cases of widespread rain, visual and statistical analyses show that PR attenuation-corrected reflectivity agrees closely with reflectivity observed from the GR composite below the melting layer. Above and within the melting layer, PR is affected critically by its sensitivity while GR beam broadening at far ranges causes systematic differences in the PR-GR comparisons. For four cases of convective rain, PR underestimates the mean reflectivities by 1-3 dB compared with those from GR at low levels where precipitation attenuation is significant toward the ground. In these cases, the low sensitivity of PR results in a small number of matched points for weak echoes. Also, the PR-GR discrepancy for the convective case is more affected by time mismatching. [ABSTRACT FROM AUTHOR]

This paper evaluates the seasonal (winter, premonsoon, monsoon, and postmonsoon) performance of seven precipitation products from three different sources: gridded station data, satellite-derived data, and reanalyses products over the Indian subcontinent for a period of 10 years (1997/98-2006/07). The evaluated precipitation products are the Asian Precipitation-Highly-Resolved Observational Data Integration Towards Evaluation of the Water Resources (APHRODITE), the Climate Prediction Center unified (CPC-uni), the Global Precipitation Climatology Project (GPCP), the Tropical Rainfall Measuring Mission (TRMM) post-real-time research products (3B42-V6 and 3B42-V7), the Climate Forecast System Reanalysis (CFSR), and the European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis (ERA-Interim). Several verification measures are employed to assess the accuracy of the data. All datasets capture the large-scale characteristics of the seasonal mean precipitation distribution, albeit with pronounced seasonal and/or regional differences. Compared to APHRODITE, the gauge-only (CPC-uni) and the satellite-derived precipitation products (GPCP, 3B42-V6, and 3B42-V7) capture the summer monsoon rainfall variability better than CFSR and ERA-Interim. Similar conclusions are drawn for the postmonsoon season, with the exception of 3B42-V7, which underestimates postmonsoon precipitation. Over mountainous regions, 3B42-V7 shows an appreciable improvement over 3B42-V6 and other gauge-based precipitation products. Significantly large biases/errors occur during the winter months, which are likely related to the uncertainty in observations that artificially inflate the existing error in reanalyses and satellite retrievals. [ABSTRACT FROM AUTHOR]

This paper describes the relationships between rainfall in Spain (1961–2010) and four teleconnection patterns on three time scales (monthly, seasonal and annual) using data from 144 meteorological stations. Spearman's test was used to carry out partial correlations, and spatial distribution maps of the correlation coefficients were generated with kriging method. We regionalise the study area into homogeneous areas containing weather stations with a similar precipitation response to the patterns. The links between precipitation and the NAO, AO and EA are generally positive in the east and negative in the west of Spain, whereas WeMO correlates positively in the north and negatively in the rest. As a general result, the winter months and winter season show the highest percentage of weather stations with statistically significant correlations. Spearman coefficients of up to 0.62 were found for the NAO, AO and EA. WeMO strongly correlates (values up to 0.55) from October to April. Five areas have been defined: centre/southwest, northwest, north, northeast, and southeast. The mode which best explains rainfall in the two western areas is the NAO; in the north, the WeMO exerts a notable influence; EA correlates better with precipitation in the two eastern zones, especially in spring, autumn and part of winter. They are better controllers of rainfall in these areas than in the whole of the study area. [ABSTRACT FROM AUTHOR]

This paper studied the behavior of 94-GHz radar reflectivity ( Z e ) with variation in the properties of low-level water clouds, such as the effective droplet radius ( r e ), geometrical thickness ( D cld ), and liquid water path (LWP), over the northwest Pacific and China. The changes in the distribution of max Z e (the largest Z e within a cloud layer) were examined in terms of variation in the cloud parameters such as small, mid and large categories, while max Z e had monomodal distributions regarding variation in r e and D cld , that appeared bimodal in the small category of LWP. It was confirmed that the small category of LWP contained both non-precipitating clouds in the incipient stage and raining clouds in the dissipating stage. Next, optically measured particle size was combined with LWP derived from the microwave measurement to classify the precipitation type. Applying max Z e and D cld to the analysis of classified precipitation types corroborated the importance of D cld for examining the occurrence of precipitation. Finally, the position of max Z e relative to the cloud top was investigated using a measure of the probability of precipitation (POP) according to variation in r e . The results showed that the Pacific and China had ‘bow’ and ‘funnel’ shapes, respectively. The emergence of these shapes according to the variation in r e was interpreted as the enhancement of Z e due to droplet collisional growth and the attenuation of Z e by the presence of large particles. Furthermore, a detailed analysis of smaller particles (<10 μm in radius) reinforced the idea of rapid, efficient particle growth in the lower part of the cloud. [ABSTRACT FROM AUTHOR]

This paper documents the characteristics of extreme precipitation events (EPEs) in the southeastern United States (SEUS) during 2002-11. The EPEs are identified by applying an object-based method to 24-h precipitation analyses from the NCEP stage-IV dataset. It is found that EPEs affected the SEUS in all months and occurred most frequently in the western portion of the SEUS during the cool season and in the eastern portion during the warm season. The EPEs associated with tropical cyclones, although less common, tended to be larger in size, more intense, and longer lived than 'nontropical' EPEs. Nontropical EPEs in the warm season, relative to those in the cool season, tended to be smaller in size and typically involved more moist, conditionally unstable conditions but weaker dynamical influences. Synoptic-scale composites are constructed for nontropical EPEs stratified by the magnitude of vertically integrated water vapor transport (IVT) to examine distinct scenarios for the occurrence of EPEs. The composite results indicate that 'strong IVT' EPEs occur within high-amplitude flow patterns involving strong transport of moist, conditionally unstable air within the warm sector of a cyclone, whereas 'weak IVT' EPEs occur within low-amplitude flow patterns featuring weak transport but very moist and conditionally unstable conditions. Finally, verification of deterministic precipitation forecasts from a reforecast dataset based on the NCEP Global Ensemble Forecast System reveals that weak-IVT EPEs were characteristically associated with lower forecast skill than strong-IVT EPEs. Based on these results, it is suggested that further research should be conducted to investigate the forecast challenges associated with EPEs in the SEUS. [ABSTRACT FROM AUTHOR]

In this paper, the Weather Research and Forecasting (WRF) Model is used to investigate the sensitivity of precipitation to soil moisture and urban areas in the Netherlands. The average output of a 4-day event during 10-13 May 1999 for which the individual days had similar synoptical forcing is analyzed. Four simulations are conducted to test the impact of soil moisture changes on precipitation. A positive soil moisture-precipitation feedback is found, that is, wet (dry) soils increase (decrease) the amount of precipitation. Three additional experiments are executed, two in which urban areas in the Netherlands are expanded and one where urban areas are completely removed. Expansion of urban areas results in an increase of the sensible heat flux and a deeper planetary boundary layer, similar to reducing soil moisture. Expanding urban areas reduces precipitation over the Netherlands as a whole, but the local response is not clear. Within existing urban areas, mean and maximum temperature increases of 0.4 and 2 K, respectively, are found under an urban coverage scenario for 2040. The ratio of evapotranspiration to precipitation (a measure of the soil moisture-precipitation feedback) in the urbanization experiments is only about one-third (23%) of that in the soil moisture experiments (67%). Triggering of precipitation, on the other hand, is relatively high in the urban expansion experiments. The effects of reduced moisture availability and enhanced triggering in the urban expansion experiments compensate each other, leading to the moderate reduction in precipitation. [ABSTRACT FROM AUTHOR]

This paper investigates how atmospheric circulation and orography affect the spatial variability of extreme precipitation in terms of depth-duration-frequency (DDF) curve parameters. To this aim, the Italian territory was considered because it is characterized by a complex orography and different precipitation dynamics and regimes. A database of 1494 time series with more than 20 years of maximum annual precipitation data was collected for the durations of 1, 3, 6, 12, and 24 h. For each data series, the parameters of DDF curves were estimated using a statistical simple scale invariance model. Hence, the combined effect of orography and atmospheric fields on parameter variability was investigated considering the spatial distribution of the parameters and their relation with elevation. The vertically integrated atmospheric moisture flux J was used as a measurement of the principal direction of the vapor transport at a given location. The analysis highlights the variability of DDF parameters and quantiles according to orography and precipitation climatology. This is confirmed by the evaluation of J modal direction over the study area. The variability of DDF parameters with mere elevation shows that maxima at high elevations seem to be upper bounded and more variable than those at lower elevations. Moreover, the mean of maximum annual precipitation of unit duration decreases with elevation. This last phenomenon is defined as 'reverse orographic effect' on extreme precipitation of short durations. [ABSTRACT FROM AUTHOR]

This paper analyzed the data of temperature and precipitation in Turpan and Nantong, in the west and east of China, respectively, during the period of 1961 –2007 by linear groWh rate, moving average methods, Mann-Kendall nonparametric and moving Ttests. The result indicated that the annual average temperature in Turpan had a linear groWh rate of 0.42 °C/10 a, while the annual average temperature in Nantong had a linear tendency of 0.48 °C/10 a. The annual average maximum temperature in Turpan with linear groWh rate of 0.16 °C/10 a was lower than 0.56 °C/ 10 a of Nantong, and the annual average minimum temperature in Turpan with linear growh rate of 0.86 °C/10 a was higher than 0.70 °C/10 a of Nantong. The annual average temperature of Turpan increasing was 7 years earlier than Nantong. The annual average maximum temperature of Turpan increasing was 5 years later than Nantong. The annual average minimum temperature of Turpan increased as same as Nantong in 1986, but the curve showed different process completely. The abrupt change year of average temperature between Turpan and Nantong were same in 1996, and the abrupt change year of average maximum temperature of Turpan was 5 years later than Nantong. For precipitation, Turpan and Nantong had the same trend of increased and decreased. The reason of almost identical trend of temperature and precipitation between Turpan and Nantong may be urbanization and population increasing influencing climate change in a small area. [ABSTRACT FROM AUTHOR]

In this paper occurrences of precipitation in Iran was analyzed according to random processes by the applying of markov chain model. In order to do that occurrence and non-occurrence of rainfall of asfezari data base for the period of 1961/3/21 to 2004/12/31 was used. This data are for 7187 pixel and 15991 days. By using markov chain model first order two state dry and wet frequency matrix was made and then by the method of maximum likelihood transmission probability matrix was developed. By Chi-square goodness data following from chosen model was confirmed. By frequently powering this matrix stable probability and daily return period of rainy and non-rainy states was estimated. Period of daily returns and non-rainy days was estimated 7 and 1 respectively. So probability of precipitation was 0.1449 and probability of non-occurrence was estimated 0.8551. Return period of precipitation with lasting 1 to 3 days was calculated for all the months. The maximum likelihood of occurrence with precipitation was in March with the amount of 0.27. The shortest return period. The Shortest return period with lasting of 1 to 2 days was in February and March with the amount of 5/6 and 3/7 respectively. [ABSTRACT FROM AUTHOR]

This paper analyses current precipitation rates (PRs) and trends over the Mediterranean Sea region and their response to global climate change scenarios. The analysis uses 0.25° gridded PRs dataset over a 13-year period (1998-2010) based on remote sensing data from the Tropical Rainfall Measuring Mission. Future scenarios use the results of six global climate models (GCMs) under four representative concentration pathway scenarios (i.e., RCP26, RCP45, RCP60, and RCP85). Results indicate that the Mediterranean Sea region displays a seasonally significant (insignificant) wetter trend during cold (hot) seasons, and exhibits annual spatial variation ranging from under 15 to over 100 mm month -1 over the period 1998-2010. Sea level pressure has two different effects on precipitation over the northern (inversely related to precipitation) versus southern (directly related to precipitation) Mediterranean Sea. However, sea surface temperature is anti-correlated with precipitation. The GCMs that describe the current Mediterranean Sea precipitation most realistically are GFDL-CM3-1, MIROC-ESM-CHEM, and HadGEM2-AO, which are used to calculate the ensemble mean for each representative concentration pathway scenario. The ensemble means realizations indicate that the study area will experience substantial drought in the 21st century. Uncertainty in the projected precipitation over the Mediterranean Sea was partitioned into four sources, of which the used scenario dominates. [ABSTRACT FROM AUTHOR]

As high-resolution climate models become increasingly complex, it should be carefully assessed to what extent the improved physics in such models justifies the large computational cost that the complexity imposes. This paper presents a detailed sensitivity study of convective precipitation characteristics to the number of prognostic moments in bulk microphysics schemes using a high-resolution convection-resolving climate model. It is shown that 1-moment and 2-moment microphysics schemes produce more similar surface precipitation characteristics for a composite of 20 real-case convective simulations in Belgium than for many idealized studies conducted before. In the baseline 2-moment scheme, size sorting of particles is counteracted by collisional drop breakup to produce mean drop sizes that are similar to those in the 1-moment version of the scheme. Hence, fallout, evaporation and surface rain rates are very similar between the two versions of the scheme. Conversely, larger sensitivities of precipitation extremes were found to the treatment of drop breakup and the shape of the particle size distributions. Consistent with previous studies, domain-averaged and peak precipitation increased monotonically with increasing breakup equilibrium diameter Deq. Further, it is shown that a negative exponential size distribution results in excessive radar reflectivities for light rain rates. Surface precipitation and the joint distribution of reflectivity and rain rate are best reproduced by a 2-moment version of the scheme that applies gamma distributions with a diagnostic shape parameter for all particles and a large Deq. However, given the large sensitivities and uncertainties associated with collisional drop breakup and size sorting, it is likely that the full potential of improved physics in a 2-moment scheme will remain underexposed as long as these processes are not better understood. [ABSTRACT FROM AUTHOR]