A research study has been communicated in Boulder this week which further support the findings in
Pielke Sr., R.A., and T. Matsui, 2005: Should light wind and windy nights have the same temperature trends at individual levels even if the boundary layer averaged heat content change is the same? Geophys. Res. Letts., 32, No. 21, L21813, 10.1029/2005GL024407.
Walters, J. T., R. T. McNider, X. Shi, W. B Norris, and J. R. Christy (2007): Positive surface temperature feedback in the stable nocturnal boundary layer, Geophys. Res. Lett., 34, L12709, doi:10.1029/2007GL029505 [see also the guest post on this subject by Dick McNider]
Klotzbach, P.J., R.A. Pielke Sr., R.A. Pielke Jr., J.R. Christy, and R.T. McNider, 2009: An alternative explanation for differential temperature trends at the surface and in the lower troposphere. J. Geophys. Res., 114, D21102, doi:10.1029/2009JD011841.
that there is a warm bias in the land surface temperatures, if they are used as a diagnostic to assess deeper layer atmospheric temperature trends. In the Klotzbach et al paper, we wrote
“……any positive forcing such as additional greenhouse gases destabilizes the boundary layer, increases its depth, and mixes warm air aloft to the surface. Thus, the warming is amplified at the surface but represents a redistribution of heat rather than accumulated heat from the additional forcing. Use of surface data in which minimum temperatures are included in the data set then leads to a direct warm bias if interpreted as a heat accumulation from both the column depth dependency and the destabilization.”
There is new information in a seminar to be presented at the David Skaggs Research Center, Room 1D403 on Wednesday, November 18, 2:00 PM by Imtiaz Rangwala of the Western Water Assessment and UCAR VSP (Visiting Scientist Program) Postdoctoral Fellow. The talk is titled
“Influence of Increasing Surface Humidity on Winter Warming at High Altitudes through the 21st Century”
The abstract reads
“This presentation will review the late 20th century climate change over the Tibetan Plateau. Studies, including this one, suggest an elevation dependent warming on the plateau, i.e. higher warming at higher elevation. I will present analyses of observed climate variables (1961-2000) and a GCM output to discuss some of the mechanisms responsible for this phenomenon. In particular, I will focus on the localized greenhouse effect of water vapor increases in the boundary layer, which will be referred as surface water vapor feedback (SWVP). SWVP appears to be the major cause of surface warming during winter, particularly at higher elevations, in the model. This is supported by greater increases in downward longwave radiation relative to outgoing longwave radiation at surface during winter. This difference is greater at higher elevations. Seasonally, observations show largest warming trend in winter when there are much greater increases in the minimum temperatures relative to the maximum temperatures. These differences are also greater at higher elevations. Cloud cover, which can significantly influence the downward longwave flux, show decreasing trends in both observations and the modeled results. Between 1950 and 2100, the model shows an elevation dependent warming trend during winter and spring. We find that (1) increases in downward longwave radiation influenced by increases in surface specific humidity during winter, and (2) increases in absorbed solar radiation influenced by decreases in snow cover extent during spring are, in part, the reasons for a large warming trend over the plateau in the model.”
The relevant text with respect to the warm bias include
“In particular, I will focus on the localized greenhouse effect of water vapor increases in the boundary layer, which will be referred as surface water vapor feedback (SWVP). SWVP appears to be the major cause of surface warming during winter, particularly at higher elevations, in the model.”
“….observations show largest warming trend in winter when there are much greater increases in the minimum temperatures relative to the maximum temperatures.”
We look forward to the appearance of this paper in the literature.