Evaluation of hydrological balance and its variability in arid and semi‐arid regions of Eurasia from ECMWF 15 year reanalysis

Abstract

Abstract:Hydrometeorological cycles over arid and semi-arid regions in mid-latitude Eurasia (the Silk Road region) were investigated using meteorological reanalysis data for the period 1979-93, available from the European Centre for Medium-range Weather Forecasts (ECMWF).Results show that seasonal changes of moisture balance in Turkey and central Asia, hereafter referred to as the western region, differ from those in the Taklimakan Desert and Loess Plateau, hereafter referred to as the eastern region. Here, we equate evaporation minus precipitation with the divergence field of the vertically integrated water vapour flux. In the western region, precipitation and positive convergence C of moisture primarily occurs during October-March. In contrast, the eastern region receives precipitation and has its positive C occurring during June-August. As a result, the eastern region has nearly simultaneous seasonal peaks in precipitation P and evapotranspiration E, whereas the western region has minimum P and maximum E in summer.The main annual moisture route for the Silk Road region is from the west to east; however, moisture also comes from the north in July. Over Turkey, moisture arrives from the west and south. In central Asia, however, most of the moisture comes from the west, the convergence peaks in March, and moisture from the south and west is also greater during this month. In the Loess Plateau, moisture enters from the west, the north, and the south, and exits to the east. In July, the peak precipitation and convergence season, all moisture flows are greater for the entire region, and a large influx of moisture from the south occurs during the summer season. The moisture from the south, the monsoonal flow, has a large interannual variability.

Snow Cover Characteristics over the Main Russian River Basins as Represented by Reanalyses and Measured Data

“…In vast areas, especially in the north of Asian Russia, snow cover monitoring has been irregular since 1990. Several studies (e.g., Yatagai 2003;Schär et al 2004) proposed to overcome the problem of sparse network observations by using outputs from modern stateof-the-art atmospheric assimilation systems. Schär et al (2004) created a statistical forecast model to predict summer river discharges in central Asia.…”

Trend and interannual variation in summer precipitation in eastern Siberia in recent decades

“…Atmospheric water budget analysis can estimate the contribution of evaporation/evapotranspiration and large‐scale moisture flux divergence to precipitation (e.g. Fukutomi et al , ; Serreze and Etringer, ; Yatagai, ). If we assume that the tendency of precipitable water in the atmosphere is negligible, the water budget equation can be simplified to state that precipitation equals the sum of evaporation/evapotranspiration and moisture flux convergence: ⟨ P ⟩ = ⟨ E ⟩ − ⟨∇ · Q ⟩, where P is precipitation, E is evaporation/evapotranspiration, ⟨∇ · Q ⟩ is the divergence of vertically integrated moisture flux, and angled brackets denote the area average.…”

Simulating the Impact of climate change on streamflow in the Tarim River basin by using a modified semi‐distributed monthly water balance model

“…Annual average rainfall will increase by 5-25% in most of the regions, but will decrease by 5-10% in some parts of the region (Ragab and Prudhomme, 2002). Using meteorological reanalysis data for the period of 1979-1993, available from the European Centre for Medium-range Weather Forecasts (ECMWF), Yatagai (2003) investigated the hydrometeorological cycles over arid and semi-arid regions in midlatitude Eurasia. In the Tarim River basin, the arid region of northwestern China, the long-term trend of the hydrological time series including air temperature, precipitation, and streamflow were detected by using both parametric and non-parametric techniques (Xu et al, 2004;Chen and Xu, 2005;Chen et al, 2007).…”