Therefore, they are critical parts of water and energy cycles, and govern the land-atmosphere interactions. Land surface heat fluxes, including latent heat flux (LHF) and sensible heat flux (SHF), link the land surface with the atmosphere by transporting land surface energy and moisture into the atmosphere. The intensifying LHF and precipitation indicate the acceleration of hydrological cycle in global terrestrial monsoon domains. Moreover, remarkable phase shifts in LHF and SHF are observed for monsoon domains during late-1990s, which are in phase with those of precipitation and monsoon strength. The increasing monsoon and precipitation on one hand favor more land surface available energy being converted into LHF on the other hand they enhance the LHF by increasing the land surface net radiation. Singular value decomposition (SVD) analyses show that monsoon strength explains 25.2% and 22.2% total covariance of LHF and SHF respectively in the first modes, and that precipitation slightly raises the percentages up to 27.8% and 24% respectively. The trends in LHF and SHF are closely linked to increasing global monsoon intensity and precipitation, especially for the monsoon domain that has annual precipitation lower than 1300 mm yr −1. Two other dominant trend patterns, (LHF−, SHF−) and (LHF+, SHF+), are observed in South African and South American monsoon domains, respectively. Moreover, the increasing rate of LHF was higher than the decreasing rate of SHF, which causes a decreased trend in Bowen ratio. During the past three decades, LHF and SHF have generally undergone a rising and decreasing trend (that is, (LHF+, SHF−)), respectively, in Asian, North African, Austrian, and South American monsoon domains.
#SENSIBLE HEAT FLUX FULL#
The dimensionless kB −1 equation is simplified for use over full canopy cover and is shown to give satisfactory estimates of H over a fully-grown wheat crop.The climatology, trends and leading modes of land surface latent heat flux (LHF) and sensible heat flux (SHF) as well as their responses to monsoon and precipitation in global land monsoon domains are presented. The equation determining kB −1 was simplified and tested over another arid site with good results however, this had a limited data set (i.e., 6 data points). The present data indicate that for partial canopy cover under arid conditions kB −1 may be a function of T s measured radiometrically. To obtain appropriate r ah-values the added resistance to heat transfer, kB −1, was allowed to vary although there is both theoretical and experimental evidence that kB −1 for vegetative surfaces can be treated as constant. This was attributed to the inability with existing data to properly evaluate the resistance to heat transfer, r ah. Application of the bulk transfer equation for the estimation of sensible heat, H, gave unsatisfactory values when compared to Bowen ratio and eddy correlation methods over a particular site. The region is quite arid and is composed primarily of bushes (∼30%) and bare soil (∼70%). Surface temperatures, T s, were estimated for a natural vegetative surface in Owens Valley, California, with infrared thermometric observations collected from an aircraft.
0 kommentar(er)
