NUCAS

What is the 

Nanjing University Carbon Assimilation System (NUCAS)?

NUCAS is an open sourced carbon cycle data assimilation system, unifying the terrestrial ecosystem model (BEPS) and atmospheric transport model (TM3), with the 4D-Var algorithm.

It enables the assimilation of multiple sources of observations, including the in-situ eddy covariance data and CO2/COS concentrations, satellite derived variables such as soil moisture (SM), vegetation optical depth (VOD), fraction of absorbed photosynthetically active radiation (FAPAR), solar-induced chlorophyll fluorescence (SIF), as well as column CO2/COS concentrations.

The development of NUCAS based on the two-leaf satellite data driven ecosystem model BEPS makes it suitable for ingesting different satellite data to constrain the ecosystem processes. The coupling with the TM3 provides the additional constraint from "top-down". In collaboration with The Inversion Lab supports the persistent update and development of the model code, as well as the adjoint code.

The first open-sourced 4D-Var carbon cycle data assimilaiton system gives scientists the ability to develop a land-atmosphere coupled data assimilation system based on the current NUCAS schme. 

NUCAS source code including the adjoint code and a README file for the version 1 is now available at GitHub. To run NUCAS, the users only need the numerical recipes code, which is affordable.