The diurnal cycle throughout the stratosphere is analyzed by AER Principal Scientist Stephen Leroy in collaboration with co-author Hans Gleisner (Danish Meteorological Institute) by applying Bayesian interpolation to Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Global Positioning System radio occultation (RO) data and three scientific applications of the analysis are introduced. First, the migrating thermal tides are analyzed with unprecedented accuracy and precision, with an uncertainty in the analysis of the vertically propagating tides ranging from 0.1 K in the lower stratosphere to 0.6 K in the upper stratosphere for an individual month of RO data and with an uncertainty in a 10-year climatological diurnal cycle a factor of 10 less. Moreover, the midlatitude trapped tide is found to be smaller than what is produced by an atmospheric model and lags the model in phase, a likely consequence of a faulty parameterization of eddy diffusivity in the upper stratosphere. Second, a clear signal of solar cycle influence on the diurnal cycle is evident in this analysis, but whether the cause is the systematic bias of ionospheric residual associated with RO retrieval or it is an actual atmospheric phenomenon is less clear. Third, RO satellites and missions that obtain inadequate coverage of the diurnal cycle will be biased by under-sampling it, whether or not subsampling weather forecasts is used to remove sampling error. The analysis of the diurnal cycle in COSMIC RO data can be used to diagnose the systematic sampling error incurred by incomplete coverage of the diurnal cycle, which is of the order of 0.2 K for a Metop-based RO climatology.
Figure: This figure shows the diurnal cycle in temperature as inferred from COSMIC-1 radio occultation data. Temperature fluctuations at solar (local) times 00, 03, 06, 09, 12, 15, 18, and 21 hours are shown as functions of latitude and height in the stratosphere. Plainly apparent are the downward propagating features over the equator. These are the “migrating atmospheric tides”. Also apparent is the mid-latitude trapped mode near the stratopause (between 40 and 50 km).
Citation: The Stratospheric Diurnal Cycle in COSMIC GPS Radio Occultation Data: Scientific Applications
S. S. Leroy, H. Gleisner
Earth and Space Science, 9(3), 2022