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Quantitatively evaluation of satellite precipitation and potential evapotranspiration products with the high resolution, wide coverage and dynamic continuity is an important foundation for drought monitoring over mainland China. This paper examined the accuracy of products and the utility of drought monitoring using the newly released long-term (more than 30 years) satellite precipitation products (climate hazards group infrared precipitation with station, CHIRPS) data version 2.0 and potential evapotranspiration products (global land-surface evaporation: the Amsterdam methodology, GLEAM) dataset. We selected standardized precipitation evapotranspiration index (SPEI) and six statistical and classification measures indexes to evaluate accuracy and the utility of CHIRPS and GLEAM-Ep (potential evapotranspiration derived from GLEAM), with China Gauge-based Precipitation Daily Analysis dataset (CGDPA) and potential evapotranspiration calculated by Penman-Monteith (PM-Ep) as evaluation reference data sets. The results showed that CHIRPS and GLEAM-Ep performed well in eastern and southwest of China. However, their performance in western China was uncertain due to the sparsity of meteorological stations. SPEIs (SPEI value calculated by the CHIRPS and GLEAM-Ep) had a good performance on drought monitoring in eastern and southwestern China. Values of correlation coefficient (CC) between SPEIs and SPEIm (SPEI value calculated by the CGDPA and PM-Ep) were more than 0.6 in southeastern China, southwestern China, the middle and lower reaches of the Yangtze River region and northern China, especially in relatively humid areas, which the correlation coefficient values were more than 0.7 and the root mean-squared error (RMSE) values were less than 0.8. In order to further evaluate the performance of SPEIs in drought monitoring at spatial and temporal scales, the SPEIs3 (SPEIs at three-month scale) and SPEIm3 (SPEIm at three-month scale) in southeastern China, southwestern China, the middle and lower reaches of the Yangtze River region and northern China were compared. SPEIs3 had a better simulation effect on the evolution process of the ratio of drought area in those regions during1981-2016. And the success ratio of simulating drought duration was about 0.93, 0.57, 0.71 and 0.81, respectively. Moreover, SPEIs3 displayed a high accuracy over the four regions in capturing drought, which was the spatial distribution of typical drought events on specific month. In conclusion, SPEI based on long-term CHIRPS and GLEAM-Ep could be applied to monitor and evaluate drought in eastern and southwestern China. This paper can provide reliable reference for monitoring and warning of drought events and water resources management in those regions. [ABSTRACT FROM AUTHOR]

Water surface evaporation is an important process in the hydrologic and energy cycles. Accurate simulation of water evaporation is important for the evaluation of water resources. In this paper, using meteorological data from the Aixinzhuang reservoir, the main factors affecting water surface evaporation were determined by the principal component analysis method. To illustrate the influence of these factors on water surface evaporation, the paper first adopted the Dalton model to simulate water surface evaporation. The results showed that the simulation precision was poor for the peak value zone. To improve the model simulation’s precision, a modified Dalton model considering relative humidity was proposed. The results show that the 10-day average relative error is 17.2%, assessed as qualified; the monthly average relative error is 12.5%, assessed as qualified; and the yearly average relative error is 3.4%, assessed as excellent. To validate its applicability, the meteorological data of Kuancheng station in the Luan River basin were selected to test the modified model. The results show that the 10-day average relative error is 15.4%, assessed as qualified; the monthly average relative error is 13.3%, assessed as qualified; and the yearly average relative error is 6.0%, assessed as good. These results showed that the modified model had good applicability and versatility. The research results can provide technical support for the calculation of water surface evaporation in northern China or similar regions. [ABSTRACT FROM AUTHOR]

Eddy covariance data are widely used for the investigation of surface-air interactions. Although numerical datasets exist in public depositories for upland ecosystems, few research groups have released eddy covariance data collected over lakes. In this paper, we describe a dataset from the Lake Taihu Eddy Flux Network, a network consisting of seven lake sites and one land site. Lake Taihu is the third largest freshwater lake (area 2,400 km2) in China, under the influence of subtropical climate. The dataset spans the period from June 2010 to December 2018. Data variables are recorded at half-hourly intervals and include micrometeorology (air temperature, humidity, wind speed, wind direction, rainfall, and water/soil temperature profile), the four components of surface radiation balance, friction velocity, and sensible and latent heat fluxes. Except for rainfall and wind direction, all other variables are gap-filled, with each datapoint marked by a quality flag. Several areas of research can potentially benefit from the publication of this dataset, including evaluation of mesoscale weather forecast models, development of lake-air flux parameterizations, investigation of climatic controls on lake evaporation, validation of remote sensing surface data products, and global synthesis on lake-air interactions. The dataset is publicly available at https://yncenter.sites.yale.edu/data-access and from Harvard Dataverse (doi: 10.7910/DVN/HEWCWM) [ABSTRACT FROM AUTHOR]

A lasting decrease in the near-surface wind speed (SWS) in China has been revealed, but a following short-term strengthening in the SWS was rarely noted. In this paper, the daily mean SWS observed datasets from 328 measurement stations in Eastern China during the period 1981–2011 were used to investigate the facts and causes of the observed short-term strengthening in winter SWS in recent decades. The major results are summarized as follows: the SWS showed a significant decrease in the last 30 years, but a short-term strengthening in SWS was observed during the winter since 2000 in Eastern China. The SWS in Eastern China showed a significant decrease of − 0.11 m s−1 decade−1 from 1981 to 1999, followed by a weak increase of 0.0008 m s−1 decade−1 from 2000 to 2011. The short-term strengthening in the SWS since 2000 was mainly induced by the changes of the pressure-gradient force (PGF), which could be attributed to the changes of the sea-level pressure (SLP) in the region (51°–69.75° N, 51.75°–111.75° E). Furthermore, the changes of the PGF during the two periods of 1981–1999 and 2000–2011 were consistent with those of the SLP in the region (51°–69.75° N, 51.75°–111.75° E). The correlation coefficient between PGF and SLP was 0.32 and 0.66 during the period 1981–1999 and 2000–2011, respectively. Therefore, the effects of the changes in SLP over the region (51°–69.75° N, 51.75°–111.75° E) on changes of SWS in the Eastern China should be significant. [ABSTRACT FROM AUTHOR]

To effectively meet growing food demands, the global agronomic community will require a better understanding of factors that are currently limiting crop yields and where production can be viably expanded with minimal environmental consequences. Remote sensing can inform these analyses, providing valuable spatiotemporal information about yield-limiting moisture conditions and crop response under current climate conditions. In this paper we study correlations for the period 2003–2013 between yield estimates for major crops grown in Brazil and the Evaporative Stress Index (ESI) – an indicator of agricultural drought that describes anomalies in the actual/reference evapotranspiration (ET) ratio, retrieved using remotely sensed inputs of land surface temperature (LST) and leaf area index (LAI). The strength and timing of peak ESI-yield correlations are compared with results using remotely sensed anomalies in water supply (rainfall from the Tropical Rainfall Mapping Mission; TRMM) and biomass accumulation (LAI from the Moderate Resolution Imaging Spectroradiometer; MODIS). Correlation patterns were generally similar between all indices, both spatially and temporally, with the strongest correlations found in the south and northeast where severe flash droughts have occurred over the past decade, and where yield variability was the highest. Peak correlations tended to occur during sensitive crop growth stages. At the state scale, the ESI provided higher yield correlations for most crops and regions in comparison with TRMM and LAI anomalies. Using finer scale yield estimates reported at the municipality level, ESI correlations with soybean yields peaked higher and earlier by 10 to 25 days in comparison to TRMM and LAI, respectively. In most states, TRMM peak correlations were marginally higher on average with municipality-level annual corn yield estimates, although these estimates do not distinguish between primary and late season harvests. A notable exception occurred in the northeastern state of Bahia, where the ESI better captured effects of rapid cycling of moisture conditions on corn yields during a series of flash drought events. The results demonstrate that for monitoring agricultural drought in Brazil, value is added by combining LAI with LST indicators within a physically based model of crop water use. [ABSTRACT FROM AUTHOR]

Potash deposits commonly accumulate in highly restricted settings at the final stage of brine evaporation. This does not mean that potash deposits are formed simply as a result of the evaporation concentration of seawater or lake water, but rather as a coupling result of particular provenance, tectonics and climate activities. In this paper, we focus on the formative mechanism of the potash deposits of Lop Nur depression in Tarim Basin to interpret the detailed coupling mechanism among provenance, tectonics and climate. In terms of the provenance of Lop Nur Lake, the water of the Tarim River which displays 'potassium-rich' characteristics play an important role. In addition, the Pliocene and Lower-Middle Pleistocene clastic beds surrounding Lop Nur Lake host a certain amount of soluble potassium and thus serves as 'source beds' for potash formation. During the late Pliocene, the Lop Nur region has declined and evolved into a great lake from the previous piedmont and diluvial fan area. Since the mid Pleistocene, the great-united Lop Nur Lake has been separated and has generated a chain system consisting of Taitema Lake, Big Ear Lake and Luobei Lake which has turned into the deepest sag in Lop Nur Lake. Dry climate in Lop Nur region has increased since the Pliocene, and became extreme at the late Pleistocene. The study implies that potash formation in Lop Nur Lake depends on the optimal combination of extreme components of provenance, tectonics and climate during a shorter-term period. The optimal patterns of three factors are generally characterized by the long-term accumulation and preliminary enrichment of potassium, the occurrence of the deepest sub-depression and the appearance of an extremely arid climate in Lop Nur region. These factors have been interacting synergistically since the forming of the saline lake and in the later stages strong 'vapor extraction' caused by extremely arid climate is needed to trigger large scale mineralization of potash deposits. [ABSTRACT FROM AUTHOR]

ABSTRACT In this paper, we present the response of actual evaporation to global warming in China based on the National Centers for Environmental Prediction-National Center for Atmospheric Research ( NCEP/ NCAR) reanalysis 1, the NCEP-Department of Energy ( NCEP/ DOE) reanalysis 2, 40-year ECMWF Re-Analysis ( ERA-40), ECMWF-Interim Re-Analysis ( ERA-Interim), Modern-Era Retrospective Analysis for Research and Applications ( MERRA), and Climate Forecast System Reanalysis ( CFSR). Rotated empirical orthogonal function ( REOF) analysis was applied to reveal the coherent pattern of the change in reanalysis evaporation ( RE). According to the first four REOF modes in NCEP/ NCAR, we subdivided China into six climatic regions, and found that RE increased significantly in central and southeast of China from 1979 to 2012, especially during the sub-period of 1985-2004. Various estimates of linear trend are statistically consistent, and most of them are significant at the 95% confidence level. Conversely, RE decreased in northern and northeast although the magnitude of decreasing trends is inconsistently among the reanalysis. Moreover, there is a general tendency of RE to increase in northwest, but mostly RE trends are not significant. In the dry northwest and northern regions, rainfall is an important factor affecting the changing of RE, while RE is less sensitive to the change of temperature. However, RE rates are dominated by temperature in the humid central and southeast regions. These results support the view that the sensitivity of RE to global warming largely depends on the environment. In view of data availability, despite the general similarity, differences exist among the various reanalysis, especially in NCEP/ NCAR and CFSR. In summary, it can be concluded that the quality of RE values is higher in central and southeast, while even greater uncertainties lie in the estimates of RE in northwest China and Qinghai-Tibet Plateau. [ABSTRACT FROM AUTHOR]

Gravity desalination is an important method for obtaining fresh water from sea ice; however, the large amount of ice that is exposed to air for long periods of time sublimates and evaporates, which results in a reduction of the freshwater resource. This paper describes a study of sea ice sublimation and evaporation performed during the winter of 2013 at the western shore of Bohai Bay, China, to determine the relationship between the amount of sublimation and evaporation and the atmospheric parameters. Substantial amounts of the Bohai sea ice sublimated and evaporated, ranging from 15 to 35 % of the total. The sublimation and evaporation amount was significantly different between the day and night and was greater in the daytime because of the relative humidity difference. Sublimation and evaporation is primarily affected by atmospheric parameters, and the amount of sublimation and evaporation exhibits a good linear relationship with the relative humidity and the wind speed; a comprehensive parameters formula was determined for the Bohai Rim in China. A 10 % increase of daily relative humidity will reduce approximately 1.5 kg/m/day of the sublimation and evaporation, and the amount of sublimation and evaporation increases by 1.76 kg/m/day when the daily wind speed increases by 1 m/s. To reduce the sublimation and evaporation and maximize the amount of this freshwater resource, gravity desalination sites should be selected where the wind speed is low and the relative humidity is high, i.e., the sea ice should be configured to reduce the adverse effects of sunlight, low humidity, and air turbulence. [ABSTRACT FROM AUTHOR]