Abstract
Based on the field observation and WRF-CLM model, the effects of Gyaring and Ngoring lakes on the short-term climate over the Yellow River source area during May to September have been studied through two experiments with and without the lakes. A backward water vapor transfer model was also employed to investigate the contribution of water vapor evapotranspiration from the Gyaring and Ngoring lakes and various surface types to the local precipitation. The results show that without the Gyaring and Ngoring lakes, the sensible heat is increased by 120%, whereas the latent heat is decreased by 58.5%, and the height of atmospheric boundary layer increases from 500 to 1,500–2,000 m during daytime over the lake area. The sum of sensible and latent heat fluxes in the lake area simulated by the experiment with and without the lakes is 185.8 and 130.3 W m−2, respectively. The precipitation amount over the lake area is significantly increased without considering the lake effect, generally by more than 20–40 mm. About 63.8% of the total precipitation in Gyaring and Ngoring lakes is contributed by the external water vapor sources. The evapotranspiration from the grassland is the secondary water vapor source for the precipitation in the Yellow River source area, and 25.2% of the total precipitation is contributed by this source. Around 4.2% of the total precipitation in the lake area is contributed by the evaporation from the Gyaring and Ngoring lakes.
Highlights
The meteorological research on the Tibetan Plateau began as a result of studies on the dynamic effects of the large-scale topography of this region, initially studying how the large-scale topography of the Tibetan Plateau dynamically deflects the atmospheric air flows and causes them to rise to discovering its significant thermal effects (Manabe and Broccoli, 1990; Yanai et al, 1992; Kutzbach et al, 1993; Zhou et al, 2014)
The Weather Research and Forecasting (WRF) model did not well capture the diurnal cycles of wind speed and precipitation and overestimated the wind speed and precipitation (Table 2) during June, July, and August with a mean overestimation of 0.58 m s−1 and 0.05 mm h−1, and such overestimation mainly occurred in nighttime (Figure 2)
During the simulation period (May to September 2013), the average sum of the sensible and latent heat fluxes in the lake area simulated by the experiment with the lake is 185.8 (130.4) W m−2, indicating that the presence of lakes leads to a considerable increase in the total amounts of heat and water vapor exchange at the land–air interface
Summary
The meteorological research on the Tibetan Plateau began as a result of studies on the dynamic effects of the large-scale topography of this region, initially studying how the large-scale topography of the Tibetan Plateau dynamically deflects the atmospheric air flows and causes them to rise to discovering its significant thermal effects (Manabe and Broccoli, 1990; Yanai et al, 1992; Kutzbach et al, 1993; Zhou et al, 2014). The important role of lakes in local weather and climate systems is attributed to their distinct hydrothermal properties from those of the surrounding land surfaces, i.e., relatively low albedo, high specific heat capacity, and small surface roughness These differences directly result in the marked differences of surface thermal conditions and the regional water/energy cycles between lake–atmosphere and land–atmosphere interfaces, which would subsequently alter the temperature and moisture structure of the ABL (Schwartz and Karl, 1990), formation of convection and cumulus clouds (Miles and Verlinde, 2005), mesoscale circulations (Segal and Arritt, 1992), and the distribution of precipitation (Laird et al, 2009). We employed the WRF model to perform numerical simulations to address the short-term climatic effect of Gyaring and Ngoring lakes on the surrounding area and a backward water vapor transfer model to investigate the contribution of water vapor evapotranspiration from various surface types to precipitation. The precipitation contributed by the evapotranspiration from each surface type was calculated, and this precipitation was referred to as surface-induced precipitation
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