Assimilation of stratospheric and mesospheric temperatures from MLS and SABER into a global NWP model

Abstract

Abstract. The forecast model and three-dimensional variational data assimilation components of the Navy Operational Global Atmospheric Prediction System (NOGAPS) have each been extended into the upper stratosphere and mesosphere to form an Advanced Level Physics High Altitude (ALPHA) version of NOGAPS extending to ∼100 km. This NOGAPS-ALPHA NWP prototype is used to assimilate stratospheric and mesospheric temperature data from the Microwave Limb Sounder (MLS) and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instruments. A 60-day analysis period in January and February 2006, was chosen that includes a well documented stratospheric sudden warming. SABER and MLS temperatures indicate that the SSW caused the polar winter stratopause at ∼40 km to disappear, then reform at ∼80 km altitude and slowly descend during February. The NOGAPS-ALPHA analysis reproduces this observed stratospheric and mesospheric temperature structure, as well as realistic evolution of zonal winds, residual velocities, and Eliassen-Palm fluxes that aid interpretation of the vertically deep circulation and eddy flux anomalies that developed in response to this wavebreaking event. The observation minus forecast (O-F) standard deviations for MLS and SABER are ∼2 K in the midstratosphere and increase monotonically to about 6 K in the upper mesosphere. Increasing O-F standard deviations in the mesosphere are expected due to increasing instrument error and increasing geophysical variance at small spatial scales in the forecast model. In the mid/high latitude winter regions, 10-day forecast skill is improved throughout the upper stratosphere and mesosphere when the model is initialized using the high-altitude analysis based on assimilation of both SABER and MLS data.

Impacts of the January 2005 solar particle event on noctilucent clouds and water at the polar summer mesopause

“…Compared to temperature data from the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) instrument (Mlynczak and Russell, 1995) the MLS temperature has a negative bias uncertainty of up to 9 K (Schwartz et al, 2008). MLS temperatures in combination with SABER data have been used in the assimilation system NOGAPS-ALPHA (Hoppel et al, 2008;Eckermann et al, 2009). A comparison of the MLS temperatures used in our study with the corresponding assimilated temperatures (not shown) does not reveal a clear pattern.…”

Longitudinal structure of stationary planetary waves in the middle atmosphere – extraordinary years

“…This dataset is used to search for the top border of the SPW1 in geopotential heights. The description of NOGAPS-ALPHA can be found in Hoppel et al (2008) and Eckermann et al (2009).…”

Parameterization of middle atmospheric water vapor photochemistry for high-altitude NWP and data assimilation

“…The background error variance for water vapor in the upper atmosphere was set large enough to ensure that the analysis was highly constrained to the observations, producing a zonal mean distribution that is nearly identical to the MLS data. For further details of the assimilation system, see Hoppel et al (2008).…”

“…The model uses the non-orographic gravity wave drag parameterization of Garcia et al (2007) with the same settings as in E2008. The T79L68 model is initialized with analyzed winds, temperature, and constituents (e.g., O 3 and H 2 O) produced by the NOGAPS-ALPHA DA component, which is described in detail by Hoppel et al (2008) and E2008. From the surface to the mid-stratosphere, these NOGAPS-ALPHA analyses are based on assimilation of conventional meteorological data sets used by the operational T239L30 system.…”