Radiation budget at Sundarban mangrove forest

Energy dynamics and i ts implication to biosphere–atmosphere exchange of CO2, H2O and
CH4 in a tropical mangrove forest canopy
D. Ganguly, M. Dey, S.K. Mandal, T.K. De, T.K. Jana_
Department of Marine Science, Calcutta University, 35, B.C. Road, Kolkata 70019, India
Received 6 September 2007; received in revised form 11 January 2008; accepted 11 January 2008
Abstract
Amount of radiant energy (short wave) available to drive biosphere–atmosphere exchange of
CO2, H2O, CH4 and for t ransfer into other energy forms were determined for a t ropical
mangrove forest at the land ocean boundary of north-east (NE) coast of Bay of Bengal from
January to December 2006. The mean annual incoming short wave radiat ion (435732.8Wm-2)
was part it ioned into 29% sensible heat , 35% latent heat , 4% ground heat , 7% physical storage
energy and 10% photosynthet ic storage energy. The mean budget closing energy flux
(68.96724.6Wm-2) or, budget error was 15.8% of incoming short wave radiat ion. In Varimax
factor analysis, budget closing energy flux showed high loading in associat ion with leaf
chlorophyll of different mangrove species, indicat ing its major role for reflect ivity of the surface
for short wave. There was significant seasonality in CO2 exchange with net primary product ivity
of 14.1 μmolm-2 s-1. The mean methane emission was found higher (7.29 μgm-2 s-1) during the
dayt ime than that of night t ime (1.37 μgm-2 s-1) with maximum methane emission rates of 36.1
and 21.1 mgm-2 s-1 in December and January, respect ively. Stepwise mult iple regression analysis
between storage energy [DHs(P)] and fluxes of CO2, CH4, H (sensible heat), HL (latent heat of
evaporat ion), DR (budget closer energy) showed that the combined explained variability for CO2
flux, evapot ranspirat ion and budget closer energy (39%) was less than that of CH4 and sensible
heat flux (46%). The extent of warming effect by CH4 and sensible heat flux was predominant
over the resultant cooling effect due to the processes such as photosynthesis, evapot ranspirat ion
and albedo. The mangrove forest with two t rademarks of low albedo and high surface roughness
was poorly coupled to the environment .
2008 Elsevier Ltd. All rights reserved.
Citation : Ganguly D. et al. (2008) Energy dynamics and its implication to biosphere–atmosphere exchange of CO2, H2O and CH4 in a tropical mangrove forest canopy, Atmospheric Environment 42, 4172–4184,
doi:10.1016/j.atmosenv.2008.01.022