Attribution of dust on Tibet warming

2010 International Workshop on Asian Summer Monsoon and Its Role in Stratosphere-Troposphere Exchange

July 21, 2010, Lhasa, China

Jianping Huang1, Xiaoming Shi, Jin Su, and Bin Chen1, College of Atmospheric Science, Lanzhou University

Corresponding to: hjp@lzu.edu.cn & http://hjp.lzu.edu.cn

Climate Change in Tibetan Plateau RegionClimate Change in Tibetan Plateau Region

In the past half-century, a lot of the Tibetan Plateau’s glaciers have retreated. As the changes continue, Tibetan Plateau’s will change the water supply for billions of people and altering the atmospheric circulation over half the planet.

Tibet Plateau (TP)

• TP functions as an important modulator of regional climate over central and southern Asian (Liu et al. 2007).

• Wang et al. (2008) found that the increase of surface temperature over Tibet Plateau in the past 50 years (about 1.8 oC) has a coherent pattern with the trend in the East Asia rainfall.

• Their numerical experiments show that atmospheric heating induced by the rising TP temperatures can enhance East Asian subtropical frontal rainfall, implying that projected future increases in TP temperatures may lead to further enhanced summer frontal rainfall in EA region.

Global and China’s surface mean temperature changes in the recent 100 years, (relative to 1961-1990 average)

（全球资料取自 HadCRUTv3 ，中国资料由王绍武提供）

Warming trends for China are significant in the recent 100 years

Comparison of long-term surface temperature trend between global and three Tibet region

Northern Tibet region is one of the strongest speedy warming area over China. Why?

Annual mean temperature trend over China

Tibetan Plateau

Mangya

0.091ºC/Year

Comparison of temperature increasing between Mangya and China

Why the warming rate of northern Tibet/taklamakan Why the warming rate of northern Tibet/taklamakan area obviously higher than the China and global ?area obviously higher than the China and global ?

Response to global warmingResponse to global warming Dust and local aerosol effect Dust and local aerosol effect

Temperature increasing during last 40 years

Mangya: 3.82ºCChina Mean: 1.82ºCGlobal Mean: 0.61ºC

Recently CALIPSO lidar observations show that dust events exist in whole year over Taklamkan desert [Liu et al., 2008].

There are heavy dust storms found in summer [Huang et al., 2007].

The impact of the Taklamakan dust storm on the radiative energy budget and the implication to the regional climate are still open questions.

Example of Taklamakan dust Tansportant to Tibet

Case StudyOn July 26, 2006, a moderate wind and dust storm in North Xinjiang and

the Tarim Basin, accompanied by localized severe dust storms, developed

and extended southward. Under the influence of this storm, a wind-blown sand and/or dust cloud persisted over northern Qinghai and Tibet through 31 July, 2006.

On July 26, 2006, a moderate wind and dust storm in North Xinjiang and the

Tarim Basin, accompanied by localized severe dust storms, developed and

extended southward. Under the influence of this storm, a wind-blown sand and/or dust cloud persisted over northern Qinghai and Tibet through 31 July, 2006.

Total backscattering coefficient measured by CALIPSO for July 31, 2006.

Taklimakan

There is dust storm over Taklimakan from July 25 Aug.1, 2006

Aerosol Index derived from AURA

The 532nm total attenuated backscattering intensity (left panels) for the green-shaded portion of each track (right panels)

Dust aerosol extinction coefficient (left panels) and orbit averaged vertical profile

Integrated dust optical depth derived from CALIPSO measurements[0.45-0.92]

effaSzz ,)(21ln2

1

z aztop

zbase

z dz

To optimize the dust aerosol single-scattering albedo and asymmetry factor used over Taklamakan region, we compare the CERES TOA solar fluxes with Fu-Liou model simulations along the CALIPSO orbit using 4 different dust aerosol types from OPAC [Hess, et al., 1998]. We found that the dust aerosol type that fits best is the transported mode.

Nucleation

mode

Accumulation

mode

Transportedmode

Coarsemode

Single-scattering albedo ()

0.9740 0.9093 0.8763 0.7118

asymmetry factor (g)

0.6521 0.7162 0.7532 0.8741

Date July 24 July 26 July 29 July 30 July 31 Mean

SW 62.19 82.6 88.46 81.69 79.25 78.83

LW 8.72 5.49 10.8 5.06 7.29 7.47

Net 70.91 88.09 99.26 86.75 86.54 86.31

Dust radiation forcing at TOA

Dust radiation forcing in Atmosphere

Date July 24 July 26 July 29 July 30 July 31 Mean

SW 12.49 15.6 14.93 14.42 13.13 14.11

LW 28.64 28.86 32.73 27.64 33.65 30.30

Net 41.13 44.46 47.66 42.06 46.78 44.41

Date July 24 July 26 July 29 July 30 July 31 Mean

SW -49.70 -67.0 -73.53 -67.27 -66.12 -64.72

LW 19.92 23.37 21.93 22.58 26.36 22.83

Net -29.78 -43.63 -51.60 -44.69 -39.76 -41.89

Dust radiation forcing at BOA

SW heating Rate

沙尘气溶胶对短波辐射有很强的吸收，强沙尘可以使沙尘层的大气加热率达到 7K/day

LW Heating Rate

冷却沙尘层，加热沙尘层下部，特别是地表

沙尘在沙尘层高度上短波的加热作用为主要作用，而对于沙尘层以下的大气则长波的加热作用占主导

Net Heating Rate

辐射强迫的不确定性分析

单次散射反照率造成的估算值的不确定性最大

辐射强迫和加热率计算的不确定性分析

加热率的不确定性分析

三个影响因子对于大气的垂直加热率的廓线形态不会有影响，只是会改变数值的大小， SSA依然是影响最大的因子

辐射强迫和加热率计算的不确定性分析

The above studies show that the dust aerosol radiative heating and effect have a significant impact on the energy budget over the Taklimakan desert and Northern Tibet.

To future understanding the attribution of Taklimakan dust on Tibet warming, we need to use the model simulation for study dust transport and radiative forcing.

Model Description

• WRF coupled with several chemical modules• Dust emission scheme is Shaw et al. (2008)’s

• Mie theory is used to calculate aerosol optical properties, like aerosol extinction coefficient, single albedo, etc.

• Complex refractive indices of dust are interpolated from data of Kandler et al. (2009).

Dust Emission & Temperature Advection

Dust event is caused by cold air owing into Tarim Basin.

Transport of Dust Aerosol

• Some dust (10% of total emission) can be transported to Tibet Plateau.

• Terrain is a controlling factor in 27th, while at other time it seems not an direct factor determining the outflow flux.

(Cross section with blue background shows outflow flux at southern lateral boundary, while purple lines are flow lines.)

www.vapor.ucar.edu

Short Wave Radiative Heating

Taklamakan Tibet

The 532 nm backscatter return signal from the CALIPSO lidar showing the vertical distribution of ABCs. (From Ramanathan et al., Nature, 2007)

The temperature change dT due to ABC solar heating at the 700 hPa (or 700 mb) level ( 3 km a.s.l. ) simulated by CCM3.The change is estimated from a 50-year average of experiment and control. The white-shaded regions are the part of the Himalayas with surface pressure less than 700 mb, that is, surface elevations are higher than 3 km. (From Ramanathan et al., Nature, 2007)

The temperature change dT due to ABC solar heating at the 700 hPa (or 700 mb) level ( 3 km a.s.l. ) simulated by CCM3.The change is estimated from a 50-year average of experiment and control. The white-shaded regions are the part of the Himalayas with surface pressure less than 700 mb, that is, surface elevations are higher than 3 km. (From Ramanathan et al., Nature, 2007)

Conclusion and Discussion

Both satellite and simulation evident that the absorption of Asian dust aerosol can cause heating atmosphere and may lead to warm local climate;

10% Taklimakan dust can be transported to Tibet and those dust

may play some role in East Asia climate changes, and need to be

investigated further;

More field dust aerosol observation need to understand the their

effect on climate and hydrological cycle over Tibet.

– Fill the gap of global climate monitoring network.

– There is no any international network (such as CEOP,BSRN, Aeronet) site in Loess Plateau yet.

– Loess Plateau is a special semi-arid land surface; & part of dust aerosol source and close to the desert.

MOTIVATION

To study cloud/aerosol effect on semi-arid climate, we developed a supper site for cloud/aerosol & climate parameters measurements.

• Boundary layer • Surface radiation • Surface fluxes • Soil parameters • Ambient air analyzers; • Aerosol optical properties;• Aerosol vertical profile • Temperature and water

vapor vertical profiles; • Sky condition

Major Instruments

This site joined the PACific Dust Experiment (PADEX)

Three sites for 2008 China-US Dust Experiment

Zhangye Mobile Site for 2008 China-US Dust Experiments (DOE/NASA Mobile Facility, US)

Jingtia Mobile Site for 2008 China-US Dust Experiments (LZU Mobile Facility, China)

TaklamkanZhangye

Jingtai

SACOL

0.88

0.90

0.92

0.94

0.96

0.98

1.00

400 500 600 700 800 900 1000 1100

Comparison of Asian Dust Single Scattering Albedoversus Saharan and Saudi Arabian Dust

BeijingAnmyon, S. KoreaDunhuang, ChinaKanpur, IndiaCape VerdeSaudi Arabia - SVBahrain

Sin

gle

Sca

tter

ing

Alb

edo

Wavelength (nm)

T. Eck et al 2004

Asian Dusts are more absorbing

Retrieved single-scattering albedo

Comparison of Terra MODIS, Aqua MODIS, Deep blue, MISR, CIMEL and MFRSR aerosol optical depths.

Instantly wind up to 28m/s, Visibility 0 m

Heavy Dust Storms (April 24, 2010)

The distribution of field observations stations in spring 2010

Minqing

Heavy Dust Storms (April 24, 2010) Heavy Dust Storms (April 24, 2010)

Thank you for your attention!

Model Description (Dust Emission Scheme)

• Use scheme of Shaw et al. (2008),

G: vertical dust fluxα: vegetation maskC: empirical constantU*: friction velocityU*t : threshold friction velocityfw: wetness factor

• Follow Han et al. 2004, Lee et al. 2003, set C as 1.4*1015 g∙cm-6∙s3

• Set u*t as 30 cm/s.

Modeling Description (Physics)

Model Description (Radiative Feedback)

• Mie theory is used to calculate aerosol optical properties, like aerosol extinction coefficient, single albedo, etc.

• Complex refractive indices of dust are interpolated from data of Kandler et al. (2009).

• Indirect effect of aerosols is not considered in this simulation.