G2.03    Incomplete collocation of sun and moon photometers with day and night time aerosol lidars

Gap detailed description

Lidar profiling of atmospheric aerosols has become important for climate research during recent decades. Moreover, the synergy between lidar profiling and co-located total-column aerosol properties provides additional insight into aerosol properties by using synergistic retrieval algorithms. For instance, using the synergy a distinction can be made between fine mode and course mode particles with height. This is important to understand radiative transfer in the atmosphere. In case a Raman lidar is collocated with a sunphotometer and/or a lunar photometer, even more additional parameters can be derived. Hence, to fully exploit the synergy between lidars and photometers, collocation between both types of instruments at the various sites is needed.

Activities within GAIA-CLIM related to this gap

This gap will not be addressed within GAIA-CLIM. However, ongoing activities in other projects will be monitored and reported on.

Gap remedy(s)

Installation of sun and/or lunar photometers with existing lidar systems is recommended. Placing lidars with existing sun and/or lunar photometers is often more difficult, since lidars are larger and more complex instruments that may have additional requirements related to the operating conditions of the laser.

Measurable outcome of success

More advanced aerosol information will become available when more lidars and sun and/or lunar photometers will be collocated.

Achievable outcomes

Organizational viability: medium.

Indicative cost estimate: medium (>1million). The actual cost of sun and/or lunar photometers is moderate.


The issue is relevant for ground based stations used for model validation and verification, as well as understanding satellite retrieval algorithms and observations. Such ground based stations are typically multi-sensor inclined and can be motivated to install additional instrumentation.



Gap risks to non-resolution

Identified future risk / impact

Probability of occurrence if gap not remedied

Downstream impacts on ability to deliver high quality services to science / industry / society

Incomplete collocation between ground based aerosol lidar and sun/lunar photometer


Missing height resolved aerosol microphysical information for radiative transfer calculations.


Work package: