English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Multi-axis differential optical absorption spectroscopy (MAX-DOAS)observations of trace gases can be strongly influenced by clouds andaerosols. Thus it is important to identify clouds and characterize theirproperties. In a recent study Wagner et al. (2014) developed a cloudclassification scheme based on the MAX-DOAS measurements themselves withwhich different "sky conditions" (e.g., clear sky, continuous clouds, brokenclouds) can be distinguished. Here we apply this scheme to long-termMAX-DOAS measurements from 2011 to 2013 in Wuxi, China (31.57° N,120.31° E). The original algorithm has been adapted to thecharacteristics of the Wuxi instrument, and extended towards smaller solarzenith angles (SZA). Moreover, a method for the determination and correctionof instrumental degradation is developed to avoid artificial trends of thecloud classification results. We compared the results of the MAX-DOAS cloudclassification scheme to several independent measurements: aerosol opticaldepth from a nearby Aerosol Robotic Network (AERONET) station and from two Moderate Resolution ImagingSpectroradiometer (MODIS) instruments, visibility derived from a visibility meter and various cloud parameters from different satelliteinstruments (MODIS, the Ozone Monitoring Instrument (OMI) and the Global Ozone Monitoring Experiment (GOME-2)). Here it should be noted that noquantitative comparison between the MAX-DOAS results and the independentdata sets is possible, because (a) not exactly the same quantities aremeasured, and (b) the spatial and temporal sampling is quite different. Thusour comparison is performed in a semi-quantitative way: the MAX-DOAS cloudclassification results are studied as a function of the external quantities.The most important findings from these comparisons are as follows: (1) most casescharacterized as clear sky with low or high aerosol load were associatedwith the respective aerosol optical depth (AOD) ranges obtained by AERONET and MODIS; (2) theobserved dependences of MAX-DOAS results on cloud optical thickness andeffective cloud fraction from satellite confirm that the MAX-DOAS cloudclassification scheme is sensitive to cloud (optical) properties; (3) theseparation of cloudy scenes by cloud pressure shows that the MAX-DOAS cloudclassification scheme is also capable of detecting high clouds; (4) for somecloud-free conditions, especially with high aerosol load, the coincidentsatellite observations indicated optically thin and low clouds. This findingindicates that the satellite cloud products contain valuable information onaerosols

Cloud and aerosol classification for 2.5 years of MAX-DOAS observations in Wuxi (China) and comparison to independent data sets