To study why, where, and when deep convection

No abstract

A new generation of high-resolution (1 km) forecast models promises to revolutionize the prediction of hazardous weather such as windstorms, flash floods, and poor air quality. To realize this promise, a dense observing network, focusing on the lower few kilometers of the atmosphere, is required to verify these new forecast models with the ultimate goal of assimilating the data. At present there are insufficient systematic observations of the vertical profiles of water vapor, temperature, wind, and aerosols; a major constraint is the absence of funding to install new networks. A recent research program financed by the European Union, tasked with addressing this lack of observations, demonstrated that the assimilation of observations from an existing wind profiler network reduces forecast errors, provided that the individual instruments are strategically located and properly maintained. Additionally, it identified three further existing European networks of instruments that are currently underexploited, but with minimal expense they could deliver quality-controlled data to national weather services in near–real time, so the data could be assimilated into forecast models. Specifically, 1) several hundred automatic lidars and ceilometers can provide backscatter profiles associated with aerosol and cloud properties and structures with 30-m vertical resolution every minute; 2) more than 20 Doppler lidars, a fairly new technology, can measure vertical and horizontal winds in the lower atmosphere with a vertical resolution of 30 m every 5 min; and 3) about 30 microwave profilers can estimate profiles of temperature and humidity in the lower few kilometers every 10 min. Examples of potential benefits from these instruments are presented.

Microwave radiometer observations are compared with various radiative transfer model calculations based on simultaneous radiosondes. This analysis uses observations from Payerne, Switzerland, in cloud free conditions during the Temperature Humidity and Cloud (TUC) experiment in winter 2003/04. The results show a systematic bias in the brightness temperatures measured by the Radiometrics profiler at 55-59 GHz, which has since been corrected in the control software. Observations at lower frequencies (22-30 GHz) in these cold conditions do not support recent proposed changes to the width of the 22.235 GHz water vapour line, although this is subject to the assumption of no residual bias in the radiosonde humidity. At intermediate frequencies (51-54 GHz), the absorption models produce large differences, which may be due to differences in oxygen line coupling and highlight the need for further laboratory measurements at low temperatures. Zusammenfassung Bodengestützte Mikrowellen-Radiometer Messungen der troposphärischen Helligkeitstemperatur werden mit Strahlungstransfer-Berechnungen verglichen, die auf gleichzeitigen Radiosondierungen beruhen. Im Vergleich werden Daten der Temperature Humidity and Cloud (TUC) Kampagne verwendet, die im Winter 2003/04 in Payerne, Schweiz, gewonnen wurden. Die Resultate zeigen systematische Fehler in den Helligkeitstemperaturen des Profilers von Radiometrics zwischen 55 und 59 GHz, die in der weiteren Datenverarbeitung berücksichtigt wurden. Im Gegensatz zu aktuellen Vorschlägen zeigen die Messungen zwischen 22 und 30 GHz bei tiefen Lufttemperaturen keinen Bedarf einer Änderung der Breite der Wasserdampf-Absorptionslinie bei 22,235 GHz. Zwischen 51 und 54 GHz gibt es große Unterschiede zwischen den geprüften Modellen, was mit Unterschieden in der Kopplung der Sauerstoff-Linien erklärt werden kann. Die Unterschiede legen weitere Labormessungen bei tiefen Temperaturen nahe.

Abstract. Ground based remote sensing systems for future observation operations will allow continuous monitoring of the lower troposphere at temporal resolutions much better than every 30 min. Observations which may be considered spurious from an individual instrument can be validated or eliminated when considered in conjunction with measurements from other instruments observing at the same location. Thus, improved quality control of atmospheric profiles from microwave radiometers and wind profilers should be sought by considering the measurements from different systems together rather than individually. In future test bed deployments for future operational observing systems, this should be aided by observations from laser ceilometers and cloud radars. Observations of changes in atmospheric profiles at high temporal resolution in the lower troposphere are presented from a 12 channel microwave radiometer and 1290 MHz UHF wind profiler deployed in southern England during the CSIP field experiment in July/August 2005. The observations chosen were from days when thunderstorms occurred in southern England. Rapid changes near the surface in dry layers are considered, both when rain/hail may be falling from above and where the dry air is associated with cold pools behind organised thunderstorms. Also, short term variations in atmospheric profiles and vertical stability are presented on a day with occasional low cloud, when thunderstorms triggered 50 km down wind of the observing site Improved quality control of the individual remote sensing systems need to be implemented, examining the basic quality of the underlying observations as well as the final outputs, and so for instance eliminating ground clutter as far as possible from the basic Doppler spectra measurements of the wind profiler. In this study, this was performed manually. The potential of incorporating these types of instruments in future upper air observational networks leads to the challenge Correspondence to: C. Gaffard (catherine.gaffard@metoffice.gov.uk) to improve the observing systems and also to exploit measurements at high temporal resolution in numerical weather prediction. These examples are intended to inform potential operational users of the changes in atmospheric structure that can be observed with the new types of observing system.