Coupling between the aerosols and hydrologic cycles

Xiaoyan Jiang Climatology course, 387H Dec 5, 2006

Outlines

Aerosols formation Why we care about the aerosols and hydrologic cycle?

The coupling between the ecosystems and the hydrologic cycle via aerosol processing What do we need to know?

What tool we can use?

What data we can use to evaluate the model results?

Future Challenges

Aerosols in the atmosphere

Aerosols formation

Secondary and Primary aerosols OXIDATION

NATURAL SOURCES Fossil Fuel Biomass Burning ANTHROPOGENIC SOURCES

Why we care about the aerosols and hydrologic cycle?

The interaction between the aerosol and meteorological variables.

1.Direct effects---reducing the amount of solar radiation that reaches the surface 2.Indirect effects ---Changing the properties of clouds Aerosols and their relationships with clouds and rainfall are one of the weakest aspects of current meteorological and climate modeling The role of aerosols in the hydrologic cycle is unknown

The coupling between the ecosystems and the hydrologic cycle via aerosol processing

Modified from Barth, et al. BAMS, 2005

What do we need to know?

Emissions Anthropogenic and natural aerosols Microphysics and chemistry (dependent on aerosol type) Transformation (removal efficiency of various aerosols) Transport away from source regions (horizontally, vertically) Effect of relative humidity (especially on cloud-scales) Precipitation events (intensity and frequency) Clouds

Changes of surface solar radiation induced by urban aerosols for 1 September 2001 based on simulations from a radiative transfer model developed by Chou and Suarez [1999].

Here ‘‘diruv’’ and ‘‘difuv’’ represent direct and diffuse UV radiation, ‘‘dirpar’’ and ‘‘difpar’’ represent direct and diffuse photosynthetically active radiation, and ‘‘dirir’’ and ‘‘difir’’ represent direct and diffuse nearinfrared radiation. The ‘‘total’’ represents the total solar radiation, and the values are shown on the right-hand axis in Wm2.

The effect of aerosols in the formation of clouds

What tool we can use?

A new fully coupled meteorology- chemistry aerosol model is being developed ----WRF-chem It is a version of WRF that simulates trace gases and particulates with meteorological fields. It allows two-way nesting to simulate the air quality and meteorological fields.

Aerosol treatments in WRF-chem

 Size distribution and composition: 

sectional size distribution; moving-center or two-moment approach for the dynamic equations for mass and number; each size bin is internally mixed

modal approach Aiken Mode Accumulation Mode Coarse Mode MOSAIC - sectional approach 0.01

0.1

1 10 particle diameter (

m

m) 100 0.01

0.1

1 10 particle diameter (

m

m) 100



composition: SO 4 , NO 3 , NH 4 , CL, CO 3 , NA, CA, other inorganics, OC, EC

 MOSAIC has 3 unique components

(Zaveri et al. 2005a,b,c):



MTEM - Multi-component Taylor Expansion Model: mixing rule for activity coefficients of electrolytes in multi-component aqueous solutions



MESA - Multi-component Equilibrium Solver for Aerosols: thermodynamic equilibrium solver for solid, liquid, or mixed phase aerosols



ASTEEM - Adaptive Step Time-split Explicit Euler Method: dynamic integration of the coupled gas aerosol partitioning differential equations

numerically efficient (reduces the # of levels of iterations and # of iterations) without sacrificing accuracy; have been compared with other techniques (Fast,2006)

Some results using the fully coupled meteorology-chemistry-aerosol model

What data we can use to evaluate the model results?

Future Challenges

Coupled model development Satellite and ground-based Measurements Physical understanding for the direct and indirect of aerosols in the atmosphere The cloud microphysics The role of secondary organic aerosols in hydrologic cycle due to the importance of water and energy cycle.

Data assimilation of air quality datasets in a coupled model Model evaluation and uncertainty assessment The feedback mechanisms

Thank You !