Interactions between tropospheric chemistry and climate model temperature and humidity biases

Temperature and humidity climatologies from the Met Office Hadley Centre climate model, HadGAM1, show a strong cold bias of up to 5 K in the extra-tropical upper troposphere/lower stratosphere and a dry bias of up to 20% in the tropical lower and mid troposphere. Removing the temperature bias alone has little effect on tropospheric ozone or methane lifetime. Removing the humidity bias alone causes a reduction in both the global annual mean tropospheric ozone burden of greater than 2% and the methane lifetime of 3.6-4.2%. The impact of removing both biases together is similar to that of removing the humidity bias alone. The choice of reanalysis product (ERA-40 or NCEP) to calculate the biases does not greatly affect the results. Radiative feedback from ozone and methane reduced some of the climate model biases without any significant change to the performance of the chemistry. Citation: O'Connor, F. M., C. E. Johnson, O. Morgenstern, and W. J. Collins (2009), Interactions between tropospheric chemistry and climate model temperature and humidity biases, Geophys. Res. Lett., 36, L16801, doi:10.1029/2009GL039152.