摘要: In situ measurements of (OH), (HO2) (square brackets denote species concentrations), and other chemical species were made in the tropical upper troposphere (TUT). (OH) showed a robust correlation with solar zenith angle. Beyond th... 展开 In situ measurements of (OH), (HO2) (square brackets denote species concentrations), and other chemical species were made in the tropical upper troposphere (TUT). (OH) showed a robust correlation with solar zenith angle. Beyond this dependence, however, (HOx) ((OH) + (HO2)) only weakly responds to variations in its source and sink species. For example, at a given SZA, (HOx) was broadly independent of the product of (O3) and (H2O). This suggests that (OH) is heavily buffered in the TUT. One important exception to this result is found in regions with very low (O3), (NO), and (NOy), where (OH) is highly suppressed, pointing to the critical role of NO in sustaining OH in the TUT. 收起