Estimates of Atmospheric Angular Momentum, Friction, and Mountain Torques during 1987–1988

Publisher Website
Google Scholar
Abstract
Atmospheric angular momentum (M), friction (TF), and mountain torques (TM) are estimated from a 13-month period of European Centre for Medium-Range Weather Forecasts (ECMWF) data. Cross-spectrum analysis between M and total torques results in high coherence and one-quarter cycle phase angles (TF + TM leading M) for timescales between 5 and 66 days, suggesting that variations of the total torque are reasonably well estimated for these slower variations. However, cross spectra between M and TF, and TM separately reveal that the relatively high coherence is present between M and TF only at periods longer than 20 days. Also comparison with other published values and the considerable lack of balance between TF + TM and M over a full year implies that our estimates of TF, based on the parameterization of surface wind stress in short-term forecasts of the ECMWF, are negatively biased. For the 13-month period, the average bias is about −15.2 Hadleys (1018 kg m2 s−2). During the period there are a few nea... Abstract Atmospheric angular momentum (M), friction (TF), and mountain torques (TM) are estimated from a 13-month period of European Centre for Medium-Range Weather Forecasts (ECMWF) data. Cross-spectrum analysis between M and total torques results in high coherence and one-quarter cycle phase angles (TF + TM leading M) for timescales between 5 and 66 days, suggesting that variations of the total torque are reasonably well estimated for these slower variations. However, cross spectra between M and TF, and TM separately reveal that the relatively high coherence is present between M and TF only at periods longer than 20 days. Also comparison with other published values and the considerable lack of balance between TF + TM and M over a full year implies that our estimates of TF, based on the parameterization of surface wind stress in short-term forecasts of the ECMWF, are negatively biased. For the 13-month period, the average bias is about −15.2 Hadleys (1018 kg m2 s−2). During the period there are a few nea...

This publication has 0 references indexed in Scilit: