Higher rainfall increases outgoing long-wave radiation

From Dr. William Gray

I have just heard that NASA has a new satellite in orbit that can directly measure CO2 content in the atmosphere and that these new measurements are beginning to show that there is a positive association between increased rainfall (from higher CO2 gas amounts) and suppression of outgoing long-wave radiation.

This is to be expected in and around the areas of precipitation ? but not necessarily in the broader global-scale areas surrounding precipitation where return flow mass subsidence is driving the water vapor radiation emission level to a lower and somewhat warmer temperature.

I and a colleague, Barry Schwartz, have been analyzing 21 years (1984-2004) of outgoing long-wave radiation on various space scales as related to precipitation differences, using data from the International Satellite Cloud Climatology Project.

We have investigated how outgoing long-wave radiation changes with variations in precipitation from NOAA reanalysis data on timescales of 3 hours, 24 hours, a month, and up to a year.

We find that on a small space scale where rainfall is occurring outgoing long-wave radiation is greatly suppressed.  But on the larger regional to global space scales, outgoing long-wave radiation rises with increasing precipitation.  This is due to increased return flow subsidence in the surrounding cloud-free and partly cloudy areas.

Globally, we are finding that net outgoing long-wave radiation increases with net increased amounts of global precipitation.  This is opposite to what most modelers have programmed into their general-circulation models and, if I?m interpreting the new NASA announcement correctly, opposite to what they are currently reporting in the media.

  • Christopher Monckton of Brenchley writes: Lindzen and Choi (2009) have recently reported that, as sea surface temperature increases, outgoing radiation from the Earth?s surface also increases, while all of the UN?s simple models show it as decreasing. The significance of this measurement is that if the outgoing radiation is escaping to space much as usual then it cannot be remaining in the atmosphere to cause warming. Dr. Gray?s results are broadly consistent with those of Lindzen and Choi.