There is an important new paper that further documents the major role of land cover/land use as a component within the climate system. It is
O. A. Tuinenburg R. W. A. Hutjes C. M. J. Jacobs P. Kabat, 2010: Diagnosis of Local Land-Atmosphere Feedbacks in India
J of Climate (in press).
The abstract reads
“Following the convective triggering potential-humidity index (CTP-HIlow) framework by Findell and Eltahir (2003a), the sensitivity of atmospheric convection to soil moisture conditions is studied for India. Using the same slab model as Findell and Eltahir, atmospheric conditions in which the land surface state affects convective precipitation are determined. For India, CTP-HIlow thresholds for land surface-atmosphere feedbacks are shown to be slightly different than for the USA.
Using atmospheric sounding data from 1975-2009, the seasonal and spatial variations in feedback strength have been assessed. The patterns of feedback strengths thus obtained have been analyzed in relation to the monsoon timing. During the monsoon season, atmospheric conditions where soil moisture positively influences precipitation are present about 25% of the time. During onset and retreat of the monsoon, the South and East of India show more potential for feedbacks than the North. These feedbacks suggest that large scale irrigation in the South and East may increase local precipitation.
In order to test this, precipitation data (from 1960-2004) of the period of about three weeks just before the monsoon onset date has been studied. A positive trend in the precipitation just before the monsoon onset is found for irrigated stations. It is shown that for irrigated stations, the trend in the precipitation just before the monsoon onset is positive for the period 1960-2004. For non-irrigated stations, there is no such upward trend in this period. The precipitation trend for irrigated areas might be due to a positive trend in the extent of irrigated areas, with land-atmosphere feedbacks inducing increased precipitation.”
The conclusion contains the text
“We conclude that the CTP-HIlow framework is a good method to efficiently determine the potential for local land-atmosphere feedbacks. Periods and regions where feedbacks are potentially important can be determined easily. Because of the limitations in the framework, a three dimensional model that takes into account more processes should be used to study the land atmosphere feedbacks in more detail. This is beyond the scope of the present paper and is a subject of further study.”
There are other papers that support their findings. These are
Niyogi, D., C.M. Kishtawal, S. Tripathi, R. S. Govindaraju, 2010, Observational Evidence that agricultural Intensification and land use change may be reducing the Indian Summer Monsoon Rainfall, Water Resources Research, 46, 3, doi:10.1029/2008WR007082, 2010.
Kishtawal C., D. Niyogi, M. Tewari, R. A. Pielke Sr., and M. Shepherd, 2010, Urbanization Signature in the Observed Heavy Rainfall Climatology over India, International Journal of Climatology, 30, published online Wiley InterScience DOI: 10.1002/joc.2044
Douglas, E.M., D. Niyogi, S. Frolking, J.B. Yeluripati, R. A. Pielke Sr., N. Niyogi, C.J. Vörösmarty, and U.C. Mohanty, 2006: Changes in moisture and energy fluxes due to agricultural land use and irrigation in the Indian Monsoon Belt. Geophys. Res. Letts, 33, doi:10.1029/2006GL026550.
Douglas, E., A. Beltrán-Przekurat, D. Niyogi, R.A. Pielke, Sr., and C. J. Vörösmarty, 2009: The impact of agricultural intensification and irrigation on land-atmosphere interactions and Indian monsoon precipitation . A mesoscale modeling perspective. Global Planetary Change, 67, 117.128, doi:10.1016/j.gloplacha.2008.12.007.
Lei, M., D. Niyogi, C. Kishtawal, R. Pielke Sr., A. Beltrán-Przekurat, T. Nobis, and S. Vaidya, 2008: Effect of explicit urban land surface representation on the simulation of the 26 July 2005 heavy rain event over Mumbai, India. Atmos. Chem. Phys. Discussions, 8, 8773.8816.
Roy, S.S., R. Mahmood, D. Niyogi, M. Lei, S.A. Foster, K.G. Hubbard, E. Douglas, and R.A. Pielke Sr., 2007: Impacts of the agricultural Green Revolution – induced land use changes on air temperatures in India. J. Geophys. Res. – Special Issue, 112, D21108, doi:10.1029/2007JD008834.