Two aspects of moisture origin relevant to analysis of isotope modeling Maxwell Kelley MIT Department of Earth, Atmospheric, and Planetary Sciences and NASA Goddard Institute for Space Studies IAEA SIMS meeting February 25-27, 2004
A Survey of Precipitation Source Distributions Back Home Figures Isotopic motivations for an examination of moisture origins: Understanding real-world isotopic records Comparing different GCM simulations: physics vs. transport Relevant aspects of moisture origin: Source temperature source latitude Extratropical targets Continentality of sources Summertime land areas
Summary and Implications of PSDs Back Home Figures Most-likely transport distances of 00 km vary relatively little geographically compared to mean TDs generally >00 km local meteorology as important as long-range moisture transport Moisture recycling prevalent, especially in continental interiors land surface feedbacks low-latitude ice cores get moisture from nearby convection (in GCM) Long-range and/or meridional transport important to many areas despite proximity of most-likely sources, but TDs somewhat smaller than in some paradigms western extratropical coasts polar ice cores Indian monsoon deep tropics
Up Back Home Figures 90 Precipitation age (days) JJA - - - -180-1 -120-60 - 0 60 90 120 1 180 0 4 8 12 16 2 6 14 18 Subtropical minima; equatorial/polar maxima Seasonality
90 6 mb DJF Up Back Home Figures Broad longitudinal range of sources for the wintertime Arctic - - - -180-1 -120-60 - 0 60 90 120 1 180 90 JJA High continental fraction for the summertime Arctic - - - -180-1 -120-60 - 0 60 90 120 1 180 0.1 0.3 0.5 0.7 0.9 0.2 0.4 0.6 0.8 1
SUMMER Up Back Home Figures Most-likely sources relatively local Nearness of most-likely source location also seen in trajectory calculations Recycling statistics place the proximity of most-likely sources into perspective Locality of sources extends to tropical ice-core targets
WINTER Up Back Home Figures θ=38 N θ=43 N θ=47 N θ=28 N Mean source locations often much more distant than most-likely sources Pineapple express not evident in time mean Prevailing winds often a poor guide to PSDs, which differ from low-level VSDs Nearby most-likely sources in interior PSDs absent in free-tropospheric VSDs
SURFACE WINTER Up Back Home Figures 8 mb 7 mb Low-level VSDs reveal precipitation intermittency, characteristic transport altitude Disparate precipitation and FTWV sources in continental interiors
Up Back Home Figures JJA 35-40% from SH DJF Meridional transport prevalent in many sectors but most-likely sources local Cold pool moisture only a modest fraction of rainy-region precipitation >60% of annual rainfall between 12 S-12 N originates within same latitude band Rainy/dry areas often distinguished by length of tails apparent in transport distance
Up Back Home Figures 90 Precipitation transport distance (km) JJA - - - -180-1 -120-60 - 0 60 90 120 1 180 10 20 40 00 2000 00 4000 00 Variations within the deep tropics reflect zonal advection Low subtropical values result from subsidence of dry air
Up Back Home Figures Summer precipitation fraction from outlined sources 90 - - Cent. U.S. R=0.2 CF=0.5 Amazon R=0.25 CF=0.49 Sahel R=0.18 CF=0.54 Eurasia R=0.15 CF=0.6 - -180-1 -120-60 - 0 60 90 120 1 180 0 0.1 0.2 0.3 0.4 0.05 0.15 0.25 0.35 0.45 Brubaker et al. (1993) Region R Amazon 75 - W, 15 S-2.5 N 0.2-0.3 Sahel W-15 E, 7.5-15 N 0.1-0.5 C. USA 5-85 W, 32.5-42.5 N 0.2-0.3 Eurasia 25-45 E, 47.5-57.5 N 0.2-0.3 Continental fractions much higher than recycling ratios
Up Back Home Figures 90 Precipitation fraction from continental sources ANN - - - -180-1 -120-60 - 0 60 90 120 1 180 0 0.2 0.4 0.6 0.8 1 0.1 0.3 0.5 0.7 0.9 Summer Region Study CF Amazon SA79 0.5 Sahel extends to coast GO96 >0.44 C. USA upper Mississippi BR01 0.7 E. Asia map NU99 >0.8
90 OCT-MAR Up Back Home Figures Annual Greenland θ 45 N Annual Antarctic θ 45 S - - - -180-1 -120-60 - 0 60 90 120 1 180 90 - APR-SEP Target Study CF θ 35 W, 71 N JO89 35 N Summit WE01 0.25 Mid-Atl. 90 S CI95 20-40 S 90 S DE00 >0.05 45 S Large latitudinal displacements compared to lower latitudes Source regions similar to those of lower free-tropospheric water vapor -40% of annual Greenland snowfall of continental origin - - -180-1 -120-60 - 0 60 90 120 1 180 0.1 0.3 0.5 0.7 0.9 0.2 0.4 0.6 0.8 1
Precipitation sources 4 mb vapor sources Up Back Home Figures 1 0.9 0.8 0.7 (a) DJF (c) DJF (b) (d) Seasonal dependence due to migration of W/E transition latitude 0.6 0.5 0.4 0.3 0.2 (e) JJA (g) JJA (f) (h) Monsoon influence strongest in the southern Himalayas 0.1 Origins of vapor at ice-core altitudes during summer are almost as local as those of the precipitation falling at GCM grid-mean surface elevation as a result of vertical transport within nearby deep convection.
Up Back Home Figures 90 Precipitation from subtropical sources (mm/day) ANN - - - -180-1 -120-60 - 0 60 90 120 1 180 0 0.4 0.8 1.3 2.2 0.2 0.6 1 1.7 2.8 Rainy zones the most likely destination of cold-pool moisture
Up Back Home Figures 90 Precipitation fraction from subtropical sources ANN - - - -180-1 -120-60 - 0 60 90 120 1 180 0 0.2 0.4 0.6 0.8 1 0.1 0.3 0.5 0.7 0.9 Destination distribution of cold-pool moisture
Up Back Home Figures Brubaker et al. (2001) Calculated from observed time-varying precipitation, reanalysis moisture fluxes, modeled evaporation
Numaguti (1999) Up Back Home Figures
JJA Back Home Figures 90 DJF MC mass flux through 4 mb (mb/day) - - - -180-1 -120-60 - 0 60 90 120 1 180 0 80 5 20 40 60 0
DJF Back Home Figures 90 JJA MC mass flux through 4 mb (mb/day) - - - -180-1 -120-60 - 0 60 90 120 1 180 0 80 5 20 40 60 0
JJA Back Home Figures 90 DJF CMAP Precipitation (mm/day) - - - -180-1 -120-60 - 0 60 90 120 1 180 0 1 3 6 0.1 2 4 8 15
DJF Back Home Figures 90 JJA CMAP Precipitation (mm/day) - - - -180-1 -120-60 - 0 60 90 120 1 180 0 1 3 6 0.1 2 4 8 15
JJA Back Home Figures 90 Precipitation (mm/day) and surface winds (m/s) DJF - - - -180-1 -120-60 - 0 60 90 120 1 180 0 1 3 6 0.1 2 4 8 15
DJF Back Home Figures 90 Precipitation (mm/day) and surface winds (m/s) JJA - - - -180-1 -120-60 - 0 60 90 120 1 180 0 1 3 6 0.1 2 4 8 15
List of Figures Back Home Figures Prec. τ 6-mb polar VSDs CMAP prec. Prec. and surface winds Wet-season continental PSDs Extratropical cold-season PSDs Extratropical cold-season VSDs Wet-season moisture recycling Annual continental fraction Tropical marine PSDs Frac. of subtrop. evap. Dest. of subtrop. evap. PSDs for Greenland and Antarctica
Author abbreviations Back Home Figures BR93 Brubaker et al. 1993 BR01 Brubaker et al. 2001 CI95 Ciais et al. 1995 DE00 Delaygue et al. 2000 GO96 Gong and Eltahir 1996 JO89 Johnsen et al. 1989 NU99 Numaguti 1999 SA79 Salati et al. 1979 SZ02 Szeto 2002 WE01 Werner et al. 2001
References Back Home Figures Brubaker, K. L., P. A. Dirmeyer, A. Sudradjat, B. S. Levy, and F. Bernal (2001). A 36-yr climatological description of the evaporative sources of warm-season precipitation in the Mississippi River Basin. J. Hydromet. 2, 537 557. Brubaker, K. L., D. Entekhabi, and P. S. Eagleson (1993). Estimation of continental precipitation recycling. J. Clim. 6, 77 89. Ciais, P., J. W. C. White, J. Jouzel, and J. R. Petit (1995). The origin of present-day Antarctic precipitation from surface snow deuterium excess data. J. Geophys. Res. 0, 18917 18927. Delaygue, G., V. Masson, J. Jouzel, R. D. Koster, and R. J. Healy (2000). The origin of Antarctic precipitation: a modelling approach. Tellus 52(B), 19 36. Gong, C. and E. Eltahir (1996). Sources of moisture for rainfall in west Africa. Water Resour. Res. 32, 3115 3121. Johnsen, S. J., W. Dansgaard, and J. W. C. White (1989). The origin of Arctic precipitation under present and glacial conditions. Tellus 41(B), 452 468.
Back Home Figures Numaguti, A. (1999). Origin and recycling processes of precipitating water over the Eurasian continent: experiments using an atmospheric general circulation model. J. Geophys. Res. 4, 1957 1972. Salati, E., A. D. Olio, E. Matsui, and J. R. Gat (1979). Recycling of water in the Amazon basin: an isotopic study. Water Resour. Res. 15, 12 1258. Szeto, K. K. (2002). Moisture recycling over the Mackenzie basin. Atmosphere-Ocean 40, 181 197. Werner, M., M. Heimann, and G. Hoffmann (2001). Isotopic composition and origin of polar precipitation in present and glacial climate simulations. Tellus 53(B), 53 71.