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Meteorological and oceanographic data from ships of opportunity are the largest contributor to the world’s ocean surface database and thus are extensively used to estimate the change in climatic properties over the world’s oceans during the previous 150 years. The importance of these data for climate change studies underscores the need to fully understand the error associated with averages of these data. The sampling error problem is especially acute for ship data due to the fact that ships are moving platforms and, thus, report observations from constantly varying locations with time. This paper develops a theoretical framework for assessing the averaged sampling error associated with monthly, 1°×1° latitude-longitude box averaged ship data. It should be noted that the time-space distribution of ships within the averaging domain strongly affects the sampling error. This is shown in our derivation. The framework developed here can be used to improve upon existing methods for estimating the sampling error associated with three-dimensional box averages of meteorological and oceanographic data obtained from ship records. The framework is complimentary to existing methods of assessing biases and random error due to instrumentation, recording, etc. It is demonstrated mathematically that the uncertainty due to incomplete sampling is primarily a trade off between of the number of observations and their relative locations within the box as well as the inherent time-space correlation structure of the variable of interest. This work differs from other studies in that the three-dimensional interdependence of data is taken into account in deriving an expression for the sampling error. [ABSTRACT FROM AUTHOR]

Summary ¶The paper deals with the computation of solar energy available in a specific location. First, a new formula describing the relation between global solar irradiation and the duration of bright sunshine is established. The analysis of its use shows that global solar clear sky irradiance models are essential tools for daily computation of global irradiation. An integrated spectral atmospheric transmittance model is presented, it can be used to compute beam and diffuse clear sky irradiance for all applications where broadband solar energy input is needed. Since it is desirable to use simplified estimation methods for many applications, a parametric global solar irradiance model, derived from the spectral model, is also presented. This model needs only surface meteorological data as input. The influence of the averaging method used for the input parameters on the model accuracy is evaluated. Comparison of model results with the measurements shows an acceptable level of accuracy with the new model. Finally, an application of daily global solar energy computation is presented. [ABSTRACT FROM AUTHOR]

Summary ¶Trends and low frequency fluctuations relying on 14 observed temperature and precipitation series 1901?1998 from Hungarian sites are presented. The statistical significances of systematic changes are calculated by the t-test for the linear trends and the Mann-Kendall test. Characteristics of long-term fluctuations are investigated by spectrum analysis (Fisher-test), fitting optimum-ranked polynomials as well as illustrated by smoothed curves of 15-point Gauss-filter application. While the increase of mean temperature in Hungary during the 20 th century is not significant, the annual precipitation totals have substantially decreased. In the first half of the century mainly the precipitation totals in the transitional seasons decreased. By the second half of the century the seasonal structure of the precipitation trends has altered significantly: there was practically no systematic change in the transitional seasons, but winter precipitation decreased dramatically. The paper makes some comparisons with the same type climatic characteristics of the surrounding geographical regions, the temperature changes of the Northern Hemisphere, as well as discusses the relationship between winter precipitation in Hungary and the North Atlantic oscillation. A significant 50-year oscillation was found in the summer mean temperatures and the annual sums of extreme positive daily temperature anomalies in Hungary. This oscillation seems to be in tune with other processes over the Euro-Atlantic region. A cycle of 3.6 years in the annual precipitation totals was found to be significant at the 0.10 level. [ABSTRACT FROM AUTHOR]

In this note we observe that a problem of linear approach to Granger causality testing between CO and global temperature is that such tests can have low power. The probability to reject the null hypothesis of non-causality when it is false is low. Regarding non-linear Granger causality, based on multi-layer feed-forward neural network, the analysis provides evidence of significant unidirectional Granger causality from CO to global temperature. [ABSTRACT FROM AUTHOR]

Based on daily air temperature data from 745 stations in China, the present study investigates the regional characteristics of temperature trend and the dependence of temperature changes on the altitude during the period of 1963-2012. There is a consistent warming trend throughout the country except for the southwest China where a cooling trend is identified. Moreover, significant warming trend exists in highland areas such as the Northeast, Inner Mongol, and the Tibet region. Compared with other seasons, the warming trend is most pronounced in highland regions in winter. In summer, the temperature has no obvious increasing trend in north China, while the cooling trend is found in south China. The relationship between altitude and temperature trend is further investigated by dividing China into three subregions according to the altitude-below 200, 200-2,000, and above 2,000 m. Although there is no simple linear relationship between elevation and warming trend on national scale, the temperature trend-altitude relation is different among the three regions. The temperature trend decreases with altitude below 200 m while increases from 200 to 2,000 m, and a weak positive temperature trend-altitude relation is found over 2,000 m. The strongest temperature trend-altitude relations are found in the subtropical regions, especially pronounced south of 36°N in China. The magnitudes of decreases from 200 to 2,000 m are one order lower than the increases below 200 m. Low-altitude stations appear to be influenced more by anthropogenic aerosols. High-altitude stations are mostly located in flat terrain and sparsely populated region. Therefore, temperature trends change with elevations. [ABSTRACT FROM AUTHOR]

A crop simulation model must first be capable of representing the actual performance of crops grown in any region before it can be applied to the prediction of climate variability and change impacts. A cropping systems model (CropSyst) simulations of crop productivity in the sub-Saharan Central African (using Cameroon as the case study) region, under the current climate were compared with observed yields of maize, sorghum, groundnut, bambara groundnut and soybean from eight sites. The model produced both over-and-under estimates, but with a mean percentage difference of only –2.8%, ranging from –0.6% to –4.5%. Based on these results, we judged the CropSyst simulations sufficiently reliable to justify use of the model in assessing crop growth vulnerability to climatic changes in Cameroon and else where. [ABSTRACT FROM AUTHOR]

Anomalies of mean air temperature of 12 consecutive months were detected recently at a number of spatial scales: from local via national and continental, to hemispheric. At all these spatial scales, pre-2007 records were exceeded by considerable margins. The recent rise in the mean temperature of 12 consecutive months at several scales has remained largely unnoticed, because the 12-month means are seldom analyzed. Broad attention is typically focused on monthly, seasonal and annual temperatures. Analysis of shifted 12-month periods helps spot peculiar 12-month episodes with remarkable temperature anomalies that do not coincide with a calendar year. Introducing 12-month running mean temperatures into the global warming debate can prove useful. [ABSTRACT FROM AUTHOR]

Tropical North African climate variability is investigated using a Sahel rainfall index and streamflow of the Nile River in the 20th century. The mechanisms that govern tropical North Africa climate are diagnosed from NCEP reanalysis data in the period 1958–1998: spatially – using composite and correlation analysis, and temporally – using wavelet co-spectral analysis. The Sahelian climate is characterised by a decadal rhythm, whilst the mountainous eastern and equatorial regions exhibit interannual cycles. ENSO-modulated zonal circulations over the Atlantic/Pacific sector are important for decadal variations, and create a climatic polarity between South America and tropical North Africa as revealed through upper-level velocity potential and convection patterns. A more localised N–S shift in convection between the Sahel and Guinea coast is associated with the African Easterly Jet. [ABSTRACT FROM AUTHOR]

Spectral analysis of geomagnetic activity, global air temperature, Earth’s rotation rate and zonal circulation, when smoothed from secular trend and periods shorter than 23 years, shows a concentration of energy around the 60-year period explaining more than 80% of the entire variance. This information has enabled the set-up of a cascade physical model that integrates the Sun-atmosphere-Earth system as a single unit and ties solar corpuscular radiation to global warming through Earth’s rotation and atmospheric circulation. Our results suggest that changes in geomagnetic activity, and in the Earth’s rotation, could be used as long- and short-term indicators, respectively, of future changes in global air temperature. [ABSTRACT FROM AUTHOR]

summary¶long-term trends in annual, seasonal, and monthly mean temperature (abbreviated as amt, smt, mmt, respectively) in japan are investigated. the magnitude of a trend is measured by assuming it to be linear. the statistical significance of a site trend is assessed by the mann-kendall (mk) with consideration of serial correlation. the statistical field significance of trends in three major climatic regions: hokkaido (i), areas adjacent to the japan sea (ii), and to the pacific ocean (iii), is evaluated by the bootstrapping test which preserves cross-correlation among sites. from 1900 to 1996, amt increased from 0.51 to 2.77 °c averaged across all 46 sites. at the regional scale, amt increased by 1.38, 1.08, and 1.32 °c in regions i, ii, and iii, respectively. the trends at both sites and regions are statistically significant even at the significance level (α) of 0.005. smt increased from 0.47 to 3.69 °c at all the 19 available sites with the highest increases in winter and spring. except for a few series, the changes in smt are statistically significant at α = 0.01. the upward trends in smt are statistically significant even at α = 0.001 in both regions ii and iii. mmt at 19 sites increased within a wide range from 0.17 to 4.12 °c. the increases are largest in the winter and spring months, and most of the site increases are statistically significant at α = 0.05. the trends are statistically significant at α = 0.025 and 0.001 in regions ii and iii, respectively. the trends in both smt and mmt in region iii are larger than those in region ii. [ABSTRACT FROM AUTHOR]

Over large parts of the Northern Hemisphere's continents temperature has been increasing during the last century. Particularly minimum temperatures show a more pronounced increase than maximum temperatures. Not only the phenological seasons, but also the potentially plant damaging late frost events are governed by the atmosphere. In case of a rise of minimum temperatures one would expect phenological phases and spring late frost events to occur earlier. In this work the question is elucidated whether plant phenology shifts at a higher or lower rate towards earlier occurrences than potential plant damaging events, like spring late frost events. Frost events based on the last occurrence of daily minimum temperatures below a certain threshold have been moving faster to earlier occurrence dates than phenological phases during the last decades at 50 climate stations in Central Europe. Trend values of frost time series range around m0.2 days/year and of phenological time series are between m0.2 and 0.0 days/year over the period from 1951-1997. 'Corylus avellana beginning of pollination' is the only one of the 13 phases considered here with a lower trend value of m0.28 days/year. Early phases are more adapted to below zero temperatures and therefore follow more closely the temperature variability. Later phases seem to have more reason to be concerned about possible late frost events and react more cautiously towards higher spring temperatures and earlier last frost dates. The risk of late frost damage for plants should have been lower during the last decade as compared to the previous decades. [ABSTRACT FROM AUTHOR]