Analysis On Land-Atmosphere Moisture-heat Characteristic In Tazhong Of The Taklimakan Desert

Based on the data observered during January, April, July, and October in 2009, this paper mainly analyzes temperature and moisture diurnal variation and vertical gradient characteristic of surface layer and soil, analyzes soil heat flux and intensity of surface heating field characteristic, and analyzes moisture-heat characteristic. Then we obtain some conclutions as follows,(1) Surface layer temperatureDiurnal change of temperature for each layers are consistent, the maximum value appears in the afternoon, and the minimum value appears before and after sunrise. There is temperature inversion phenomenon in the surface layer at night. The temperature in cloudy and sandy is lower than the temperature in sunny day.(2) Surface layer moistureMean specific moistures are 0.85～0.97g/kg,1.97～2.02g/kg,5.14～5.29g/kg,1.85～1.96g/kg during January, April, July, and October. There is moisture inversion phenomenon in the surface layer, the maximum intensity occurs in October, the minimum one occurs in April, and the intensity of moisture inversion at night is stronger than which in day. The maximum moisture appears in sandy day, then is sunny day, and the minimum one occurs in cloudy day.(3) Soil temperatureSoil temperature is manifested as sine curve. The surface temperature has the largest amplitude of change rate, the deeper the less obvious, and there is no obvious diurnal variation signal at the 40cm depth. Peak surface temperature appears at 13, the valley one appears in the before and after sunrise. Soil temperature in cloudy and sandy day is higher than which in sunny day.(4) Soil moistureSoil moisture is ranged from 0.01% to 0.1%. The largest one is observed in April, about 0.07%, and the lowest one is shown in October, about 0.02%. 2.5cm soil has minimum moisture. There is the pool area of water vapor between the sand layer 10cm and 20cm depth in January and April, and it is shown that the above layer is dry, and the layer bellow is wet in July and October. The maximum soil moisture appears in cloudy day, followed by sandy, and the minimum one is observed in sunny day.(5) Soil heat fluxThe total soil heat flux is negative in January and October with upward direction, and is positive in April and July with downward direction. Surface soil heat flux is positive during 09-16 in January, 07-14 in April, 07-16 in July, and 08-14 in October, and heat is transported from surface to down, while during other times the transmission of heat is upward. There are heat dissipation and heat sink layer in the shallow sand layer during the daytime. Weather conditions have a great effect on soil heat flux, especially in the surface soil heat flux.(6) Intensity of surface heating fieldThe rates of surface soil heat flux in net radiation in January, April, July, and October are 44.91%, 9.15%, 8.12%, and 11.25%.Intensity of surface heating field is positive during daytime. Relative to the atmosphere, the surface is the strong heat source. In January, April, and July the surface is a weak cold source at night, and in October the surface is a weak heat source before mid night, and is a weak cold source after mid night. The peak of intensity of surface heating field is at 12 in January, July, and October, and appear at 13 in April, which are expressed as 112.74Wm-2,244.78Wm-2,170.42Wm-2,and 274.16Wm-2, respectively. In different weather conditions, the surface is a strong heat source during the daytime; surface is a weak heat source before mid night, and is a weak cold source in after mid night in sunny and sandy; the surface is a weak cold source at night in cloudy.