Description

Land-atmosphere interactions are a main driver of Earth's surface water and energy budgets. The importance of the land surface is rather intuitive, and has been demonstrated not only in terms of predictability on daily to seasonal timescale (Betts et al. (2017) [24]), but also in terms of influencing extremes such as drought and heatwaves (Paimazumder and Done (2016) [158]), PBL evolution and cloud formation (Milovac et al. (2016) [140]) and afternoon convection (Guillod et al. (2015) [75]), and tropical cyclone re-intensification (Andersen and Shepherd (2014) [5]). Other linkages, such as the role of soil moisture (SM) or vegetation heterogeneity in mesoscale circulation (Hsu et al. (2017) [96]) and planetary waves (Koster et al. (2014) [110]), and those driven by land use and land cover change or management (Hirsch et al. (2015) [90]; Findell et al. (2017) [59]) are topics of active research.

Figure 1 is a schematic of local land-atmosphere interactions in a quiescent synoptic regime, including the soil moisture-precipitation (SM-P) feedback pathways (Ek and Mahrt (1994) [51]; Ek and Holtslag (2004) [50] ). Solid arrows indicate a positive feedback pathway, and large dashed arrows represent a negative feedback, while red indicates radiative, black indicates surface layer and PBL, and brown indicates land surface processes. Thin red and grey dashed lines with arrows also represent positive feedbacks. The single horizontal gay-dotted line (no arrows) indicates the top of the PBL, and the seven small vertical dashed lines (no arrows) represent precipitation

Figure 1: Local Land-atmosphere Interaction (courtesy of Michael Ek)

Recently, the land surface updates in 2017 GFS operational physics includes:

IGBP 20-type 1-km land classification
STASGO 19-type 1-km soil classification
MODIS-based snow free albedo
MODIS-based maximum snow albedo
Diurnal albedo treatment
Unify snow cover, albedo between radiation and land surface model
Increase ground heat flux under deep snow
Upgrade surface layer parameterization scheme GFS Surface Layer Scheme to modify the roughness-length formulation and introduce a stability parameter constraint in the Monin-Obukhov similarity theory to prevent the land-atmosphere system from fully decoupling leading to excessive cooling of 2m temperature during sunset

Figure 2: Land Data Sets Used in NCEP Modeling Systems

Intraphysics Communication

Argument Table

General Algorithm

lsm_noah::lsm_noah_run