GASSP uses data "levels" based on terminology widely used in remote sensing:
However, because requirements differ for specific applications, GASSP has instead supported the development of the Community Intercomparison Suite (CIS; www.cistools.net; WatsonParris et al.
In situ measurements at ground sites are particularly important data in GASSP. To quantify the potential spatial sampling errors in a typical continental environment, we used a high-resolution model to simulate "measurements" and compared them with spatially averaged fields representing a 100-km-scale global model grid cell (Schutgens et al.
The objective of this aspect of GASSP was to quantify global model uncertainty caused by uncertain processes and emissions and then to explore how in situ aerosol measurements can help to reduce this uncertainty and determine what effect this has on aerosol radiative forcing.
One objective of GASSP is to understand which sources of uncertainty in a model can be constrained by particular measurements.
The first approach was to simply select a small number of simulations from the GLOMAP ensemble that best match the GASSP measurements (Fig.
Further work is now underway to relate all the measurement types in GASSP to their effectiveness at constraining the modeled radiative forcing.
This is an important discovery of the GASSP project--that even a tightly constrained global aerosol model can still generate a wide range of aerosol radiative forcings even though the change in aerosols directly causes the forcing, and we have assumed that the uncertainty in the simulated forcing comes only from the aerosol component of the model.
The extensive GASSP aerosol database combined with the perturbed parameter ensembles provides an optimum way to detect such structural errors.
GASSP set out to understand and reduce uncertainty in model simulations of aerosol radiative forcing caused by the uncertainties in the aerosol component of the model.
GASSP has created a harmonized dataset of nearly a quarter of a century of aerosol in situ measurements comprising over 46,000 measurement hours from aircraft and ships and from over 300 surface sites (Fig.
Aerosol measurements are highly diverse and difficult to harmonize (the GASSP database includes 70 measured aerosol variables).