西北干旱区夏季强干、湿事件降水环流及水汽输送的再分析

为深入分析西北内陆干旱区夏季降水的主要水汽源地及其输送通道,首先,梳理和评述了过去50年西北干旱区水汽输送的研究进展和问题;接着,利用国家气象局信息中心近50年的实测降水及NCEP/NCAR再分析资料等,挑选更多有代表性的强干、湿日(月)事件,再进行环流和水汽输送的对比分析。主要结论如下:(1)过去西北干旱区各地的干、湿环流研究共识多,进展快;而水汽输送分析依旧众说纷纭。(2)过去的水汽输送分析联系降水环流不够;针对西北干旱区降水特点不够;还应加进数值模拟等分析手段。(3)在本文诊断分析和先前数值模拟基础上,指出西北内陆旱区夏季降水的主要水汽源地在东南沿海一带,它借助西行台风、西伸了的西太平洋副热带高压及柴达木低压等多个天气系统和西太平洋副热带高压西南侧东南风急流、西侧南风低空急流及河西偏东风等三支气流的次第密切配合,首先,水汽被输送到四川盆地;接着,被北输到西北区东部;继而,再被接力西输到河西走廊及南疆盆地东部。谓之"三支气流+两个中转站的三棒接力"式水汽输送模型。它是夏季输向西北内陆旱区的主要水汽输送通道。     

Variations of contemporary glaciation of the northern slope of the Greater Caucasus in the 20th century and the forecast of its degradation in the 21st century

In the 20th century on the territory of the northern slope of the Greater Caucasus the number of glaciers increased by 245 (or by 19%) and the glaciation area decreased by 849 km² (or by 52.6%). It is revealed that the increase in the number of glaciers occurred as a result of the disintegration of larger glaciers into smaller parts and as a result of the cutoff of their tributaries, and the decrease in the glaciation area, due to the negative balance of the mass of glaciers. The length of all glaciers decreased by 128–3520 m during that period. It is demonstrated that in 1970–2011 the decrease in the glaciation area occurred with the rate being smaller than in 1895–1970 by 1.6 times that is associated with more favorable climatic conditions in 1970–2011. According to the computations of the climate model by the Main Geophysical Observatory (moderate scenario) for 2011–2099, average annual air temperature will increase by 1.06–2.70°C and the annual amount of precipitation, by 2.09–2.77%. According to the results of computations, the glaciation area in 2011–2099 will reduce by 585 km² or by 76.5%. In the region under consideration, glaciation with the area of 180 km² which will be concentrated only in the central part of the Greater Caucasus will maintain by 2099. The glacier runoff will decrease by 74–80%.     

Multiyear simulation of the African climate using a regional climate model (RegCM3) with the high resolution ERA-interim reanalysis

This study examines the ability of the latest version of the International Centre for Theoretical Physics (ICTP) regional climate model (RegCM3) to reproduce seasonal mean climatologies, annual cycle and interannual variability over the entire African continent and different climate subregions. The new European Center for Medium Range Weather Forecast (ECMWF) ERA-interim reanalysis is used to provide initial and lateral boundary conditions for the RegCM3 simulation. Seasonal mean values of zonal wind profile, temperature, precipitation and associated low level circulations are shown to be realistically simulated, although the regional model still shows some deficiencies. The West Africa monsoon flow is somewhat overestimated and the Africa Easterly Jet (AEJ) core intensity is underestimated. Despite these biases, there is a marked improvement in these simulated model variables compared to previous applications of this model over Africa. The mean annual cycle of precipitation, including single and multiple rainy seasons, is well captured over most African subregions, in some cases even improving the quality of the ERA-interim reanalysis. Similarly, the observed precipitation interannual variability is well reproduced by the regional model over most regions, mostly following, and sometimes improving, the quality of the ERA-interim reanalysis. It is assessed that the performance of this model over the entire African domain is of sufficient quality for application to the study of climate change and climate variability over the African continent.     

Complex study of characteristics of a Cb cloud developing over the Arabian Peninsula under high dew point deficit in the atmosphere. Part 1. Field observations and numerical modeling

Basing on airmass motion trajectory calculations over the Arabian Peninsula on April 10, 2008, it can be assumed that in the lower and middle troposphere, zones with increased air moisture exist due to air inflow from the Red Sea. As a result, mesoscale volumes of dry and moist air are neighboring, though large-scale field is comparatively homogeneous with low humidity. In the mesoscale zones, intense thunderstorm and hailstorm Cb clouds developed, whose characteristics and evolution are studied in the paper. Continuous radar observations of the clouds are carried out during 5 hours. Numerical simulation of the cloud evolution is performed with nonstationary 1.5-dimensional model. It is noted that under the mentioned atmospheric conditions, in the area under consideration, heavy rain and hail from the Cb clouds are observed. The main factors of their origination are high thermal instability of the atmosphere and moist air inflow from outside.     

Sensitivity of the regional climate model RegCM4.2 to planetary boundary layer parameterisation

This study investigates the performance of two planetary boundary layer (PBL) parameterisations in the regional climate model RegCM4.2 with specific focus on the recently implemented prognostic turbulent kinetic energy parameterisation scheme: the University of Washington (UW) scheme. When compared with the default Holtslag scheme, the UW scheme, in the 10-year experiments over the European domain, shows a substantial cooling. It reduces winter warm bias over the north-eastern Europe by 2 °C and reduces summer warm bias over central Europe by 3 °C. A part of the detected cooling is ascribed to a general reduction in lower tropospheric eddy heat diffusivity with the UW scheme. While differences in temperature tendency due to PBL schemes are mostly localized to the lower troposphere, the schemes show a much higher diversity in how vertical turbulent mixing of the water vapour mixing ratio is governed. Differences in the water vapour mixing ratio tendency due to the PBL scheme are present almost throughout the troposphere. However, they alone cannot explain the overall water vapour mixing ratio profiles, suggesting strong interaction between the PBL and other model parameterisations. An additional 18-member ensemble with the UW scheme is made, where two formulations of the master turbulent length scale in unstable conditions are tested and unconstrained parameters associated with (a) the evaporative enhancement of the cloud-top entrainment and (b) the formulation of the master turbulent length scale in stable conditions are systematically perturbed. These experiments suggest that the master turbulent length scale in the UW scheme could be further refined in the current implementation in the RegCM model. It was also found that the UW scheme is less sensitive to the variations of the other two selected unconstrained parameters, supporting the choice of these parameters in the default formulation of the UW scheme.     

Integrated indicators-based gradation of cultivated land quality in mountainous region of Southwestern China

1 Introduction The gradation of cultivated land is to assess the suitability of cultivated land for agricultural production in terms of natural and economic prop-erties of land (Feng et al. 2004). It can be used to evaluate sustainability of land use and …     

Modeling a Shore Profile Formed by Storm Cycle Impact

Oceanology - A model is developed for predicting the sand shore profile formed by storm event impact. The model takes into account the cumulative effect of elementary processes responsible for...     

Long-term variability of UV radiation in the spectral range of 300–380 nm in Moscow

The seasonal and interannual variability of global ultraviolet (UV) radiation in the spectral range of 300-380 nm (0380) in Moscow in 1968-2014 is analyzed. The effect of cloudiness on the magnitude of 0380 is assessed. The smallest (-22...-26%) losses due to cloudiness are registered in May-August, and the highest ones (to -45%) are observed in October-November. According to the UV radiation reconstruction model and measurement data, the long-term deviations of 0380 from the average (for 1968-1997) due to clouds can reach + (11-12)%. The statistically significant positive linear trend in total annual 0380 is revealed from the data of both the reconstruction model and observations (about 1.5% per decade for 1968-2014 and 3% per decade for 1979-2014).     

Gas mixing with aqueous solution in the ore-forming hydrothermal process: an example of gold

The mixing of gas and aqueous fluid in hydrothermal ore-forming processes is discussed with reference to gold deposits to demonstrate that this phenomenon may affect ore deposition. Data on fluid inclusions in samples from the Sukhoi Log and Olimpiadinskoe deposits in Russia are utilized to demonstrate possible implications of gas mixing with hydrothermal solution when gold ores are formed. A simplified thermodynamic model is suggested to show how interaction between aqueous saline solutions with pure carbon dioxide or carbon dioxide—methane mixture may affect gold solubility. Further studying such processes may provide interesting information for understanding the genesis of ore mineralization.