DOI: 10.6078/d16h6k
title: Data for: Radiative feedbacks on land surface change and associated tropical precipitation shifts

description: Changes in land surface albedo and land surface evaporation modulate the
 atmospheric energy budget by changing temperatures, water vapor, clouds,
 snow and ice cover, and the partitioning of surface energy fluxes. Here
 idealized perturbations to land surface properties are imposed in a global
 model to understand how such forcings drive shifts in zonal mean
 atmospheric energy transport and zonal mean tropical precipitation. For a
 uniform decrease in global land albedo, the albedo forcing and a positive
 water vapor feedback contribute roughly equally to increased energy
 absorption at the top of the atmosphere (TOA), while radiative changes due
 to the temperature and cloud cover response provide a negative feedback
 and energy loss at TOA. Decreasing land albedo causes a northwards shift
 in the zonal mean intertropical convergence zone (ITCZ). The combined
 effects on ITCZ location of all atmospheric feedbacks roughly cancel for
 the albedo forcing; the total ITCZ shift is comparable to that predicted
 for the albedo forcing alone. For an imposed increase in evaporative
 resistance that reduces land evaporation, low cloud cover decreases in the
 northern mid-latitudes and more energy is absorbed at TOA there; longwave
 loss due to warming provides a negative feedback on the TOA energy balance
 and ITCZ shift. Imposed changes in land albedo and evaporative resistance
 modulate fundamentally different aspects of the surface energy budget.
 However, the pattern of TOA radiation changes due to the water vapor and
 air temperature responses are highly correlated for these two forcings
 because both forcings lead to near-surface warming.
description: Output is saved as monthly averaged netcdf output from coupled
 CESM (CAM5-SLIM) simulations.
description: Time series are comprised of monthly mean values. Files marked
 *.cam.* are atmospheric output, while *.clm2.* are land output from SLIM.
 Averages of all fields (including those without time series) are provided
 in the files marked *_annual_avg* (single time slice) or *_year_avg*
 (average of each month, ie 12 time slices). Atmospheric
 (CAM) variables are described in the CESM documentation, e.g.
 here:<br>
 https://www.cesm.ucar.edu/models/cesm1.0/cam/docs/ug5_0/hist_flds_fv_cam5.html Land (SLIM) variables are described in the SLIM model source code on github at https://github.com/marysa/SimpleLand/wiki and in the SLIM documentation in Laguë et al. 2019:<br> <br> Laguë, M. M., Bonan, G. B., & Swann, A. L. S. (2019). Separating the Impact of Individual Land Surface Properties on the Terrestrial Surface Energy Budget in both the Coupled and Uncoupled Land–Atmosphere System. <i>Journal of Climate</i>, <i>32</i>(18), 5725–5744. https://doi.org/10.1175/jcli-d-18-0812.1   Experiment names are as follows: global_a2_cv2_hc0.1_rs200_cheyenne : albedo=0.2, evaporative resistance = 200s/m global_a2_cv2_hc0.1_rs100_cheyenne : albedo=0.2, evaporative resistance = 100s/m global_a1_cv2_hc0.1_rs200_cheyenne : albedo=0.1, evaporative resistance = 100s/m global_a3_cv2_hc0.1_rs100_cheyenne : albedo=0.3, evaporative resistance = 100s/m global_a2_cv2_hc0.1_rs30_cheyenne : albedo=0.2, evaporative resistance = 30s/m