Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Modelling chemistry in the nocturnal boundary layer above tropical rainforest and a generalised effective nocturnal ozone deposition velocity for sub-ppbv NOx conditions
AU - Pugh, Thomas
AU - Ryder, James
AU - Mackenzie, Rob
AU - Moller, Sarah J.
AU - Lee, James D.
AU - Helfter, Carole
AU - Nemitz, Eiko
AU - Lowe, Douglas
AU - Hewitt, C. N.
PY - 2010/4
Y1 - 2010/4
N2 - Measurements of atmospheric composition have been made over a remote rainforest landscape. A box model has previously been demonstrated to model the observed daytime chemistry well. However the box model is unable to explain the nocturnal measurements of relatively high [NO] and [O-3], but relatively low observed [NO2]. It is shown that a one-dimensional (1-D) column model with simple O-3-NOx chemistry and a simple representation of vertical transport is able to explain the observed nocturnal concentrations and predict the likely vertical profiles of these species in the nocturnal boundary layer (NBL). Concentrations of tracers carried over from the end of the night can affect the atmospheric chemistry of the following day. To ascertain the anomaly introduced by using the box model to represent the NBL, vertically-averaged NBL concentrations at the end of the night are compared between the 1-D model and the box model. It is found that, under low to medium [NOx] conditions (NOx < 1 ppbv), a simple parametrisation can be used to modify the box model deposition velocity of ozone, in order to achieve good agreement between the box and 1-D models for these end-of-night concentrations of NOx and O-3. This parametrisation would could also be used in global climate-chemistry models with limited vertical resolution near the surface. Box-model results for the following day differ substantially if this effective nocturnal deposition velocity for ozone is implemented; for instance, there is a 9% increase in the following days peak ozone concentration. However under medium to high [NOx] conditions (NOx > 1 ppbv), the effect on the chemistry due to the vertical distribution of the species means no box model can adequately represent chemistry in the NBL without modifying reaction rate coefficients.
AB - Measurements of atmospheric composition have been made over a remote rainforest landscape. A box model has previously been demonstrated to model the observed daytime chemistry well. However the box model is unable to explain the nocturnal measurements of relatively high [NO] and [O-3], but relatively low observed [NO2]. It is shown that a one-dimensional (1-D) column model with simple O-3-NOx chemistry and a simple representation of vertical transport is able to explain the observed nocturnal concentrations and predict the likely vertical profiles of these species in the nocturnal boundary layer (NBL). Concentrations of tracers carried over from the end of the night can affect the atmospheric chemistry of the following day. To ascertain the anomaly introduced by using the box model to represent the NBL, vertically-averaged NBL concentrations at the end of the night are compared between the 1-D model and the box model. It is found that, under low to medium [NOx] conditions (NOx < 1 ppbv), a simple parametrisation can be used to modify the box model deposition velocity of ozone, in order to achieve good agreement between the box and 1-D models for these end-of-night concentrations of NOx and O-3. This parametrisation would could also be used in global climate-chemistry models with limited vertical resolution near the surface. Box-model results for the following day differ substantially if this effective nocturnal deposition velocity for ozone is implemented; for instance, there is a 9% increase in the following days peak ozone concentration. However under medium to high [NOx] conditions (NOx > 1 ppbv), the effect on the chemistry due to the vertical distribution of the species means no box model can adequately represent chemistry in the NBL without modifying reaction rate coefficients.
KW - Nocturnal boundary-layer
KW - Ozone
KW - NOx
KW - Rainforest
KW - Box model
KW - ADJOINT SENSITIVITY-ANALYSIS
KW - ATMOSPHERIC SURFACE-LAYER
KW - CHEMICAL KINETIC SYSTEMS
KW - REACTIVE TRACE GASES
KW - DRY DEPOSITION
KW - BOX MODEL
KW - VERTICAL PROFILES
KW - RADICAL CHEMISTRY
KW - DECIDUOUS FOREST
KW - NITROGEN-DIOXIDE
U2 - 10.1007/s10874-011-9183-4
DO - 10.1007/s10874-011-9183-4
M3 - Journal article
VL - 65
SP - 89
EP - 110
JO - Journal of Atmospheric Chemistry
JF - Journal of Atmospheric Chemistry
SN - 0167-7764
IS - 2-3
ER -