Long term Observations minus Background monitoring of ground-based microwave radiometer network. Part 1: Brightness Temperatures
| Autor: | Ulrich Löhnert, James Hocking, Francisco Navas-Guzmán, Francesco De Angelis, Olivier Caumont, Alexander Haefele, Henk Klein-Baltink, Domenico Cimini, Bernhard Pospichal, Pauline Martinet, Jean-Charles Dupont |
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| Rok vydání: | 2017 |
| Předmět: |
Radiometer
010504 meteorology & atmospheric sciences Meteorology Planetary boundary layer Microwave radiometer Numerical weather prediction 01 natural sciences Standard deviation law.invention Atmospheric radiative transfer codes Data assimilation law Radiosonde Environmental science 0105 earth and related environmental sciences Remote sensing |
| Popis: | Ground-based microwave radiometers (MWRs) offer the capability to provide continuous, high-temporal resolution observations of the atmospheric thermodynamic state in the planetary boundary layer (PBL) with low maintenance. This makes MWR an ideal instrument to supplement radiosonde and satellite observations when initializing numerical weather prediction (NWP) models through data assimilation. State-of-the-art data assimilation systems (e.g., variational schemes) require an accurate representation of the differences between model (background) and observations, which are then weighted by their respective errors to provide the best analysis of the true atmospheric state. In this perspective, one source of information is contained in the statistics of the differences between observations and their background counterparts (O-B). Monitoring of O-B statistics is crucial to detect and remove systematic errors coming from the measurements, the observation operator, and/or the NWP model. This work illustrates a 1-year O-B analysis for MWR observations in clear sky conditions for an European-wide network of six MWRs. Observations include MWR brightness temperatures (TB) measured by the two most common types of MWR instruments. Background profiles are extracted from the French convective scale model AROME-France before being converted into TB. The observation operator used to map atmospheric profiles into TB is the fast radiative transfer model RTTOV-gb. It is shown that O-B monitoring can effectively detect instrument malfunctions. O-B statistics (bias, standard deviation and root-mean-square) for water vapor channels (22.24–30.0 GHz) are quite consistent for all the instrumental sites, decreasing from the 22.24 GHz line center (~ 2–2.5 K) towards the high-frequency wing (~ 0.8–1.3 K). Statistics for zenith and lower elevation observations show a similar trend, though values increase with increasing air mass. O-B statistics for temperature channels show different behaviour for relatively transparent (51–53 GHz) and opaque channels (54-58 GHz). Opaque channels show lower uncertainties ( |
| Databáze: | OpenAIRE |
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