Atmospheric conditions featuring the summer over the WM - PowerPoint Presentation

Atmospheric conditions featuring the summer over the WM
Atmospheric conditions featuring the summer over the WM

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Synoptics and dynamics Long Term Mean Climatological overview Possible impacts of the NAO on atmospheric pollution over the WM First evaluation of the climatological conditions during Summer ID: 414754 Download Presentation

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2012 nao slp summer nao 2012 summer slp conditions air 2014 med hpa 2013 naoi wind anomalies anomaly winds

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Slide1

Atmospheric conditions featuring the summer over the WM

Synoptics and dynamics – Long Term Mean Climatological overview.Possible impacts of the NAO on atmospheric pollution over the WM.First evaluation of the climatological conditions during Summer Charmex campaigns – 2012, 2013, and 2014.

1Slide2

H

L

L

L

H

H

H

Azores High

Thermal low – West African Monsoon

Saharan High – Subtropical High

SLP

GPH – 500

hPa

GPH – 850

hPa

GPH – 700

hPa

Summer synoptic conditions over the WM (LTM 1981-2010) Slide3

Hadley and Walker

circulations affecting the Med. Basin

African Monsoon

Asian Monsoon

3Slide4

Closed cell circulation of the Asian Monsoon

depicted by the vertical zonal cross section averaged over the 20-35°N latitudinal band of wind vectors for July-August (NCEP/NCAR LTM 1957-98) (from: Ziv, et al., 2004).

The WM is further away from the descending branch of the Asian Monsoon cell leading to weaker subsidence

4

Walker Cell - Asian Monsoon

Inversion in the winds (upper level subsidence vs. low-level rising air) is distinctly different for both basins!

Western Mediterranean

Eastern MediterraneanSlide5

Subsiding air masses over the WM is tenfold weaker as compared to the EM!

(0.1 – 1 cm s-1 )

Both combined cell circulations result in a weaker subsiding air masses as compared to the EM possibly acting as lid for dispersion of pollutants over the Med. Basin.

Downdraft

Updraft

Updraft generated by the West African Monsoon

5

1.0

0.1

Jun-Aug. LTM Omega vertical motion (Pa s

-1

) at 850

hPa

(NCEP/NCAR LTM (1981-2010)Slide6

Air mass transport – Climatology JJA 1981-2010

Wind Vector – 1.5 km

Wind Vector – 5.5 km

Wind Vector – 3.0 km

Wind Vector – 9.0 km

1 – 4 m/s

13 – 16 m/s

10 – 13 m/s

6 – 8 m/s

6

Stronger mid-

tropospheric

flow over the WMSlide7

7

Atmospheric dispersion and transport conditions over both Med. Basins during summer (NCEP/NCAR Reanalysis LTM)

Subsiding air mass bases

Western Med.

Eastern

Med.

Asian

Monsoon – Walker Cell

4.5 km

1.0 km

Omega

850hPa Downdraft motion0.1 cm s-1

1.0 cm s-1Wind Vector 3-5.5 km

8 – 11 m s-1 6 – 8 m s-1

The WM is characterized by weaker subsiding conditions and stronger

winds at mid-tropospheric layers.Slide8

NAO +

NAO -

This winter type oscillation controls the strength and direction of westerly winds and storm tracks across the north Atlantic.

Beside climatic conditions NAO affects climatic derived conditions (i.e., air pollution transport)

8

Possible impacts of the NAO on atmospheric pollution over the WM.Slide9

9

Composite means and anomalies of meteorological parameters characterizing extreme NAO+ and NAO- years over the WM over the 65-yr recordSlide10

10

SLP composite means and anomalies for JJA NAOI extreme summers (1950-2014)

NAOI

83

= 1.26

NAOI

94

= 1.07

Mean (1983,1994)

SLP slightly higher over the WM

NAOI

2012

= - 1.61

NAOI

2009

= - 1.18

SLP slightly lower over the WM

NAO

+

NAO

-

Anomaly = Mean

83,94 – LTM1981-2010

Mean (2009, 2012)

Anomaly = Mean

09,12 – LTM1981-2010Slide11

11

(From: Allan, R. J., and T. J. Ansell, 2006:  J. Climate, 19, 5816–5842.) 

The positions of SLP anomalies for the 2 highest NAO

+

and NAO

-

years derived are consistent with the study of Allan and Ansell based on 122-y (1881-2003)

NAO

+

NAO

+

NAO

-

NAO

-Slide12

12

U

925

composite means and anomalies for JJA NAOI extreme summers (1950-2014)

NAO

+

NAO

-

Slightly weaker zonal wind over the WM

Slightly stronger zonal wind over the WM

Mean (1983,1994)

Mean (2009, 2012)

Anomaly (1983,1994)

Anomaly (2009, 2012)Slide13

13

T

925

composite means and anomalies for JJA NAOI extreme summers (1950-2014)

NAO

+

NAO

-

Slightly warmer air over the WM

Much warmer air over the WM

Mean (1983,1994)

Mean (2009, 2012)

Anomaly (1983,1994)

Anomaly (2009, 2012)Slide14

New

results

from

Pierre

Nabat

Dust

outbreaks

and

weather regimes

NAO-

Atlantic

Low

/ NAO +

Blocking

Atlantic

Ridge

Dust

AOD

Sea

level

pressure

Summer

(JJA)

weather

regimes

(anomalies

) / Climatologies 1980/2012Slide15

Conditions during Summer ChArMEx

campaigns – JJA Composite Means and Anomalies for 2012, 2013, and 2014.15

Sea-level pressure

700

hPa

Zonal Wind

925 hPa

Air Temperature Slide16

SLP Mean: Jun-Aug 2012

SLP

Anom

: Jun-Aug 2012

Anomaly = Mean

2012

– LTM

1981-2010

NAO = - 1.61

Deepening of the Icelandic low and withdrawal west and weakening of the Azores High, whole Med. Basin more cyclogenetic.

Negative SLP anomalies over the Med. Basin.

Summer 2012

16

Sea-Level PressureSlide17

SLP Mean: Jun-Aug 2013

SLP

Anom

: Jun-Aug 2013

Anomaly = Mean

2013

– LTM

1981-2010

NAO = 0.72

Intensification and progression eastward of the Azores High and less cyclogenetic conditions over WM.

Positive SLP anomalies over the Western Med. Basin.

Summer 2013

17

Sea-Level PressureSlide18

SLP Mean: Jun-Aug 2014

SLP

Anom

: Jun-Aug 2014

Anomaly = Mean

2014

– LTM

1981-2010

NAO = - 0.81

Near normal strength and position of the Azores High.

Slight negative SLP anomalies over the Western Med. Basin.

Summer 2014

18

Sea-Level PressureSlide19

Stronger zonal wind comp. (3 km) during NAO

- summers (2012, 2014)Weaker zonal wind comp. (3 km) over the basin during NAO+

summer (2013)

19

700

hPa

Mean - 2012

700

hPa

Mean - 2014

700

hPa

Mean - 2013

U

700

composite means for JJA

NAOI for summer 2012/13/14 Slide20

20

925

hPa

Temp

Anom

. 2012

925

hPa

Temp

Anom. 2014925

hPa Temp Anom. 2013Colder air temperature over the WM during NAO

+ summer (2013)

Warmer air temperature over the WM during NAO- summer (2012)

Air TemperatureSlide21

Daily

weather

regimes

in

2012

Summer

2012

NAO –

Blocking

Atlantic Ridge

Atlantic Low / NAO +Slide22

22

Large-scale atmospheric dispersion and transport conditions

are favored

over

the WM

contrary to

the EM.

In spite of the summer NAO (SNAO) smaller variability and spatial extent, extreme SNAO suggest that:

SNAO- : WM more

cyclogenetic, stronger winds, warmer as compared to SNAO+

Summer 2012 (NAOI = -1.6) Weak Azores High, Med. Basin more cyclogenetic than its summer LTM as indicated by stronger zonal winds at mid-

tropos. and warmer air temp.

Summer 2013 (NAOI = 0.72) Eastward penetration of Azores High, less cyclogenetic conditions over W. Med., weaker winds at mid-

tropos. and colder air temp.

Summer 2014 (NAOI = -0.81). Slightly lower SLP, slightly stronger zonal winds over the W. Med.

Very preliminary conclusions….Slide23

The following slide exposes the possible issues for the discussion

23Slide24

24

Is the first statement true and does it hold for all summers? Is the second statement true ?

If indeed true, can this rule of thumb be turned upside down by internal climate variability (e.g. NAO)?

Can we point on the responsible for the unexpected low pollution concentration (emitting sources/ diluting conditions) in 2012,13 and 14?

Do we have enough pollutants data to

assess

if these conditions differ much for 2012, 2013 and 2014?

1. Large-scale atmospheric dispersion and transport conditions

are favored over

the WM contrary to

the EM: The WM is characterized by weaker subsiding conditions and stronger winds. 2. Summer NAO

- years favor dispersion and transport over the WM: More cyclogenetic and stronger winds.

Shom More....