The atmospheric hydrologic cycle over the Arctic basin from reanalyses. Part I: Comparison with observations and previous studies

The atmospheric moisture budget is evaluated for the region 70 degrees N to the North Pole using reanalysis datasets of the European Centre for Medium -Range Weather Forecasts (ECMWF; ERA: ECMWF Re-Analysis) and the collaborat ive effort of the National Centers for Environmental Prediction (NCEP) and the National Center for Atmospheric Research (NCAR). For the forecast field s of the reanalyses, the ERA annually averaged P - E (precipitation minus e vaporation/sublimation) field reproduces the major features of the basin pe rimeter as they are known, while the NCEP-NCAR reanalysis forecast fields c ontain a spurious wave pattern in both P and E. Comparisons between gauge d ata from Soviet drift camp stations and forecast P values of the reanalyses show reasonable agreement given the difficulties (i.e., gauge accuracy, tr anslating location). When averaged for 70 degrees-90 degrees N, the ERA and NCEP-NCAR forecast P - E are similar in the annual cycle. Average reanalys is forecast values of E for the north polar cap are found to be 40% or more too large based on comparisons using surface latent heat flux climatologie s. Differences between a synthesized average moisture flux across 70 degrees N from rawinsonde data of the Historical Arctic Rawinsonde Archive (HARA) an d the reanalysis data occur in the presence of rawinsonde network problems. It is concluded that critical deficiencies exist in the rawinsonde depicti on of the summertime meridional moisture transport. However, it remains to be seen whether the rawinsonde estimate can be rectified with a different m ethod. For 70 degrees-90 degrees N, annual moisture convergence (P - E) val ues from the ERA and NCEP-NCAR are very similar; for both reanalyses, annua l P - E values obtained from forecast fields are much lower than those obta ined from moisture flux convergence by about 60%, indicating severe nonclos ure of the atmospheric moisture budget. The nonclosure primarily results fr om anomalously large forecast E values. In comparison with other studies, r eanalyses moisture convergence values are much more reasonable. A synthesis of the reanalysis moisture convergence values and more recent studies yiel ds a value of 18.9 +/- 2.3 cm yr(-1) for the north polar cap.