Atmospheric NO₃: 1. Measurement technique and the annual cycle at 40°N

Abstract

The nitrate radical abundance is often measured by making use of its strong absorption of visible radiation in a band near 662 nm. We show that this NO 3 absorption feature has strong negative correlation with water vapor, which requires that water vapor absorption be explicitly considered in attempts to measure NO 3 from the ground. Concurrent observation of a second, weaker NO 3 feature near 623 nm provides an independent means of confirming and quantifying the accuracy of the measurement. These considerations are included in the analysis of a full year of nighttime stratospheric NO 3 data at 40°N. The observations are in good general agreement with theoretical predictions and do not support the existence of a stratospheric scavenger for NO 3 .