Ensemble spread and its implication for the evaluation of temperature trends from multiple radiosondes and reanalyses products

Abstract

Based on the ensemble spread, a methodology of measuring uncertainty in weather forecasts, the temperature trend and spread have been estimated using five radiosonde data sets and seven reanalysis products beginning in 1989. The results show that the magnitude of warming or cooling depends on the data sources, atmospheric heights, and geophysical latitudes. Over low‐middle latitudes, the cooling varies from −2.6 K/decade in NCEP‐DOE to −0.8 K/decade in HADAT2 in the lower stratosphere. The warming weakly changes from 0.2 through 0.4 K/decade in the middle troposphere. Over Antarctica, there is a pronounced warming in the low‐middle troposphere in the three NCEP reanalyses and the RATPAC radiosonde data sets, and cooling in the other eight products. Over the Arctic, the warming is observed from the lower troposphere to the lower stratosphere in all twelve data sets. Significant cooling is identified over the middle stratosphere (above 50 hPa) in all five radiosondes. For global mean temperature, the trend is approximately 0.2 K/decade in the troposphere and −0.8 K/decade in the stratosphere. The spread increases significantly with atmospheric height from approximately 0.1 K/decade at 850hPa to 0.8 K/decade at 30hPa. The spread in the reanalysis data sets is much larger than in the radiosondes in the stratosphere. In contrast, the spread in both the reanalysis and radiosondes data sets is very small and shows the trend in better agreement with each other in the troposphere.