Analogue correction method of errors and its application to numerical weather prediction

In this paper, an analogue correction method of errors （ACE） based on a complicated atmospheric model is further developed and applied to numerical weather prediction （NWP）. The analysis shows that the ACE can effectively reduce model errors by combining the statistical analogue method with the dynamical model together in order that the information of plenty of historical data is utilized in the current complicated NWP model, Furthermore, in the ACE, the differences of the similarities between different historical analogues and the current initial state are considered as the weights for estimating model errors. The results of daily, decad and monthly prediction experiments on a complicated T63 atmospheric model show that the performance of the ACE by correcting model errors based on the estimation of the errors of 4 historical analogue predictions is not only better than that of the scheme of only introducing the correction of the errors of every single analogue prediction, but is also better than that of the T63 model.

Sensitivity analysis of standardized precipitation index to climate state selection in China

In the calculation of the standardized precipitation index(SPI)index,it is necessary to select a certain period of precipitation samples as the reference climate state,and the SPI obtained by different reference climate states have different size.Therefore,the influence of different reference climate states on the accuracy of SPI calculation is worth analyzing.Based on the monthly precipitation data of 1184 stations in China from 1961 to 2010,the influence of the selection of the reference climatic state in the calculation of SPI was analyzed.Using 30 consecutive years as the duration of the reference climatic state,1961-2010 is divided into three periods 1961-1990,1971-2000.1981-2010.Taking the SPI obtained from the entire period as the standard value,the spatial distribution of SPI error and the accuracy of SPI classification based on each reference period were analyzed.Then,the resampling method was used to analyze the influence of time-continuous precipitation samples on the size of SPI.The results show that the SPI error of most sites is less than 0.2,and the accuracy of SPI classification is more than 80%.Although the errors of SPI mostly come from extreme drought and extremely wet,this does not affect the accuracy of the recognition of extreme drought and extremely wet.In most regions,it is reliable to calculate SPI based on the precipitation data of continuous 30 years,but the reliability of SPI is relatively low in areas with frequent drought.The results of the resampling analysis and 30-year sliding analysis show that the distribution parameters have noticeable turning characteristics,and the precipitation distribution parameters of nearly 85%stations had noticeable turning point before 1985,which led to the precipitation data of continuous 30 years easily overestimate the dry/wet.

Investigation of environmental and land use impacts in forested permafrost headwaters of the Selenga-Baikal river system,Mongolia-Effects on discharge,water quality and macroinvertebrate diversity

Headwater streams play a major role for provision of ecosystem services,e.g.drinking water.We investigated a high-altitude headwater catchment of the Kharaa River(including 411st-order rivers)to understand the impact of land cover(especially forest cover),environment and human usage on runoff,chemical water quality and macroinvertebrate fauna in a river basin under discontinuous permafrost conditions in an arid,sparsely populated region of Mongolia.To verify our hypotheses that different landuses and environmental impacts in permafrost headwaters influence water quality,we investigated 105 sampling sites,37 of them at intermittent stream sections without water flow.Discharge was positively impacted by land cover types steppe,grassland and forest and negatively by shrubland,forest burnt by wild fires(indicating a reduction of permafrost)and slope.Water quality was affected by altitude,longitude and latitude,shrub growth and water temperature.Shannon diversity of macroinvertebrates was driven by water temperature,iron content of the water,flow velocity,and subbasin size(adjusted R^(2)=0.54).Sample plots clustered in three groups that differed in water chemistry,macroinvertebrate diversity,species composition and bio-indicators.Our study confirms that steppes and grasslands have a higher contribution to runoff than forests,forest cover has a positive impact on water quality,and diversity of macroinvertebrates is higher in sites with less nutrients and pollutants.The excellent ecological status of the upper reaches of the Kharaa is severely threatened by forest fires and human-induced climate change and urgently needs to be conserved.

On statistical energy functions for biomolecular modeling and design

Statistical energy functions are general models about atomic or residue-level interactions in biomolecules, derived from existing experimental data. They provide quantitative foundations for structural modeling as well as for structure-based protein sequence design. Statistical energy functions can be derived computationally either based on statistical distributions or based on variational assumptions. We present overviews on the theoretical assumptions underlying the various types of approaches. Theoretical considerations underlying important pragmatic choices are discussed.