| Autor: |
Natalia Chubarova, Julian Gröbner, Yelena Nezval, Atsumu Ohmura |
| Rok vydání: |
2013 |
| Předmět: |
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| Zdroj: |
AIP Conference Proceedings. |
| ISSN: |
0094-243X |
| Popis: |
We present the results of continuous longwave downwelling irradiance (LDI) monitoring in Moscow from April 2008 to March 2012, which has been in operation at the Meteorological Observatory of Moscow State University (MSU MO). The measurements are carried out within wavelength range 3.5-50 μm using a precision infrared radiometer (PIR) which is regularly calibrated against international standards and tested in the Physical Meteorological Observatory in Davos (Switzerland) with accuracy comparable to the BSRN measurements (2-4 W/m2). According to these measurements the impact of various atmospheric factors on LDI has been assessed. For clear sky conditions we estimated the effects of temperature T and water vapor content W (cm). Water vapor content was evaluated from Cimel sunphotometer data (AERONET) in the 940 nm channel. A simple equation is proposed to retrieve the LDI in the absence of cloudiness and aerosol optical thickness at 500 nm (AOT500) less than 0.7 which has been compared with the results of other parameterizations. In conditions with a smoky aerosol with extremely high aerosol optical thickness the LDI dependence on AOT500 should be taken into account. According to our results the effect of extremely high AOT500 of about 5-6 provides an LDI increase of about 50 Wm−2 or 10-15%. The analysis of cloud effects reveals a significant growth of LDI in cloudy conditions up to 30% during daytime and up to 25% at night. The upper layer thin cloudiness does not affect LDI. On average, annual LDI in Moscow was 301 Wm−2 with seasonal changes of about 130 Wm−2 due to variations mainly in temperature and cloud cover. For the entire observation period the LDI changed from 424 Wm−2 in July 2009, to 136 Wm−2 in February 2012. Maximum LDI values were observed under optically thick low layer cloudiness. Minimum LDI values were observed in clear sky conditions and low temperatures. The average LDI daily range is 18-33 Wm−2 in summer and 6-18 Wm−2 in winter conditions. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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