Statistical analysis of HONO and relative humidity time series measured in the EGER-Project
Matthias Sörgel1, Ivonne Trebs2, Alexander Moravek2, Franz X. Meixner2, Cornelius Zetzsch1
1 Atmospheric Chemistry Research Laboratory, University Bayreuth
2 Max-Planck- Institute for Chemistry, Mainz
2 Max-Planck- Institute for Chemistry, Mainz
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The HONO concentrations measured with two LOPAPs (LOng Path Absorbtion Photometer) at the Waldstein-Weidenbrunnen site in north eastern Bavaria, Germany (50°09’N, 11°52’E, 775m above sea level) during field campaigns of the EGER-Project (Exchange processes in a mountainous region) are related to humidity. On timescales of about one week this is due to low and high pressure areas causing dry or rainy weather. During dry periods HONO concentrations rise continuously aside the diurnal cycle to maximum values of about 500ppt at night, whereas rain events cause an (almost complete) washout, down to 15-20 ppt. But also on a 10min scale (~ time resolution of the LOPAP instruments) the HONO concentration and humidity signals show a good congruence. In order to gain more detailed insights into often discussed relative humidity dependence of HONO formation process, we have applied Singular Spectrum Analysis (SSA) (Kondrashov and Ghil 2006) to HONO and humidity time series measured during intensive operating periods of the EGER-Project. The SSA was used as a gap filling method to obtain continuous time series for applying cross correlation function. The analytical step of the SSA gains information about the main frequencies of the time series like weekly or diurnal variations. For comparison the same analysis was done for NO2 and HONO. Spatio-temporal filling of missing points in geophysical data sets; D. Kondrashov and M. Ghil; Nonlinear Processes in Geophysics;2006; 13; 151-159
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