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Institute of Energy and Climate Research

# LOPAP

LOng-Path AbsorPtion

Nitrous acid (HONO) is an important precursor for radicals in the atmosphere. It plays a crucial role in the tropospheric budgets of OH and HOx. HONO measurements are difficult since high sensitivity in the ppt range has to be combined  with the absence of cross sensitivities.

LOPAP  (LOng-Path AbsorPtion) is a very sensitive technique to measure HONO in the troposphere. At BU Wuppertal, Germany, LOPAP was developed and used in field and laboratory experiments. In 2007, we developed a LOPAP instrument for mobile applications. This instrument was certified for Zeppelin flights. A further, identically constructed instrument is used at the atmosphere simulation chamber SAPHIR.