TY - JOUR A1 - Li, Lanqian A1 - Žagar, Nedjeljka A1 - Raeder, Kevin A1 - Anderson, Jeffrey L. T1 - Comparison of temperature and wind observations in the Tropics in a perfect‐model, global EnKF data assimilation system Y1 - 2023-07-04 VL - 149 IS - 755 SP - 2367 EP - 2385 JF - Quarterly Journal of the Royal Meteorological Society DO - 10.1002/qj.4511 PB - John Wiley & Sons CY - Ltd N2 -

Flow‐dependent errors in tropical analyses and short‐range forecasts are analysed using global observing‐system simulation experiments assimilating only temperature, only winds, and both data types using the ensemble Kalman filter (EnKF) Data Assimilation Research Testbed (DART) and a perfect model framework. The idealised, homogeneous observation network provides profiles of wind and temperature data from the nature run for January 2018 using the National Center for Atmospheric Research (NCAR) Community Earth System Model (CESM) forced by the observed sea‐surface temperature. The results show that the assimilation of abundant wind observations in a perfect model makes the temperature data in the Tropics largely uninformative. Furthermore, the assimilation of wind data reduces the background errors in specific humidity twice as much as the assimilation of temperature observations. In all experiments, the largest analysis uncertainties and the largest short‐term forecast errors are found in regions of strong vertical and longitudinal gradients in the background wind, especially in the upper troposphere and lower stratosphere over the Indian Ocean and Maritime Continent. The horizontal error correlation scales are on average short throughout the troposphere, just several hundred km. The correlation scales of the wind variables in precipitating regions are half of those in nonprecipitating regions. In precipitating regions, the correlations are elongated vertically, especially for the wind variables. Strong positive cross‐correlations between temperature and specific humidity in the precipitating regions are explained using the Clausius–Clapeyron equation.

UR - http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/11585 ER -