BALANCING THE ATMOSPHERIC HYDROLOGIC BUDGET

The atmospheric hydrologic budget in an idealized general circulation model is difficult to balance, especially if samples are too infrequen t, mainly because of an inaccurately determined moisture flux divergen ce. Although the climatology can be reasonably derived by considering longer time averages, the aliased anomalous moisture divergences due t o insufficient sampling are intrinsic and cannot be removed; the effec t is noticeable and detrimental out to seasonal timescales. Increased temporal resolution or even continuous accumulations are really requir ed. Lack of temporal resolution also affects forecast skill as well as the perceived importance of the precipitable water tendency. Current atmospheric hydrologic analyses of moisture fluxes and even satellite precipitation observations may have similar sampling problems. We reco mmend that modern analyses should provide more frequently sampled or e ven continuously accumulated hydrologic quantities, just as precipitat ion is currently provided.