Possible Effects of Possible Effects of Global Warming on Global - PowerPoint PPT Presentation

Possible Effects of Possible Effects of Global Warming on Global Warming on Global Warming on Global Warming on Tropical Cyclone Tropical Cyclone Activity Activity Johnny Chan Guy Carpenter Asia Guy Carpenter Asia- -Pacific Climate Impact Centre Pacific Climate Impact Centre School of Energy and Environment School of Energy and Environment City University of Hong Kong City University of Hong Kong

Outline Outline � � Background Background � � Relationship between global warming and Relationship between global warming and frequency of intense tropical cyclone frequency of intense tropical cyclone occurrence occurrence � � Variations of tropical cyclone Variations of tropical cyclone characteristics in the western North characteristics in the western North Pacific Pacific � � Summary Summary Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 1

Background Background � � Global warming leads to Global warming leads to an increase in the temperature near the earth’s an increase in the temperature near the earth’s – – surface (land and ocean) surface (land and ocean) an increase in the amount of water vapour in the an increase in the amount of water vapour in the – – atmosphere due to an increase in ocean temperature atmosphere due to an increase in ocean temperature and a higher atmospheric temperature capable of and a higher atmospheric temperature capable of and a higher atmospheric temperature capable of and a higher atmospheric temperature capable of holding more water vapour holding more water vapour � � No study has definitively demonstrated that the No study has definitively demonstrated that the dynamic factors are modified by global warming dynamic factors are modified by global warming (although some have suggested an increase in (although some have suggested an increase in vertical wind shear). vertical wind shear). Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 2

Background Background � � Due to global warming, the thermodynamic Due to global warming, the thermodynamic factors have become more favourable for factors have become more favourable for tropical cyclone formation and development. tropical cyclone formation and development. � � To determine whether global warming has an To determine whether global warming has an impact on the frequency of occurrence of impact on the frequency of occurrence of impact on the frequency of occurrence of impact on the frequency of occurrence of tropical cyclones or of intense cyclones, we tropical cyclones or of intense cyclones, we need to examine whether the thermodynamic need to examine whether the thermodynamic factors are related to the variations on such factors are related to the variations on such frequencies. frequencies. � � A good proxy of the thermodynamic factors is A good proxy of the thermodynamic factors is the Maximum Potential Intensity (MPI) the Maximum Potential Intensity (MPI) Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 3

Background Background • MPI = f(ocean temperature, outflow temperature, net amount of energy available for convection) • Because MPI gives the maximum possible intensity, a higher value of MPI summed over the ocean basin and over a season should imply a more thermodynamically energetic atmosphere, and more TCs could reach higher intensities ∴ a season with a higher value of MPI ∴ ∴ ∴ should have more intense TCs if the dominant control is thermodynamic Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 4

Atlantic 6 68 Cat45 66 5 NCEP MPI 64 4 r of Cat45 62 PI Number o MP 3 3 60 2 58 1 56 0 54 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Year Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 5

Western North Pacific 12 74 Jul-Nov Cat45 NCEP MPI 72 10 70 8 68 t45 Cat4 PI MP 6 6 66 4 64 2 62 0 60 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Year Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 6

21 21- -year running correlations with NCat45 year running correlations with NCat45 Ocean Basin Ocean Basin Period Period Correlation Correlation Correlation Correlation (best track) (best track) (Kossin et al. 2007) (Kossin et al. 2007) Atlantic 1960-2007 0.45 1970-2007 0.59 1980-2007 0.63 1979-2006 0.61 0.61 Western North Pacific 1960-2007 -0.01 1970-2007 -0.06 1980-2007 -0.08 1981-2006 -0.13 -0.36 Eastern North Pacific 1960-2007 0.29 1970-2007 0.35 1980-2007 0.34 South Indian Ocean 1981-2007 0.35 South Pacific 1981-2007 0.03 Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 7

21-year running correlations of MPI with NCat45 21 21-year running correlations with NCat45 year running correlations with NCat45 0.8 0.6 0.4 0.2 0.2 0.0 -0.2 -0.4 Atlantic WNP ENP -0.6 1980 1985 1990 1995 2000 2005 Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 8

Summary Summary � � Thermodynamic control on the frequency Thermodynamic control on the frequency of intense TCs is important of intense TCs is important only only in the in the Atlantic Atlantic � � Estimating the effect of global warming on � Estimating the effect of global warming on � Estimating the effect of global warming on Estimating the effect of global warming on the frequency of intense TCs therefore the frequency of intense TCs therefore must also assess such an effect on the must also assess such an effect on the dynamic processes. dynamic processes. Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 9

Western North Pacific Western North Pacific Tropical Cyclones Tropical Cyclones Tropical Cyclones Tropical Cyclones Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 10

Number and Intensity Number and Intensity Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 11

Annual Number of TCs and Intense TCs in the WNP Annual Number of TCs and Intense TCs in the WNP Annual number of TSs and Cat45 TCs over the WNP 40 14 TS 10-yr filtered TS 12 Cat45 35 10-yr filtered Cat45 10 30 8 6 25 4 20 2 15 0 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 12

Webster et al.’s (2005) Webster et al.’s (2005) Science Science paper paper Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 13

No. of Category 4 and 5 Typhoons No. of Category 4 and 5 Typhoons 1975-89 1990-2004 Number 75 115 Percentage 32 42 Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 14

No. of Category 4 and 5 Typhoons No. of Category 4 and 5 Typhoons 1960-74 1975-89 1990-2004 Number 105 75 115 Percentage 37 32 42 Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 15

ACE vs.. ACE vs.. VORT VORT, , SHEAR SHEAR and and MSE MSE Science , 311, 1713b, Tellus 2007 3.0 ACE 2.5 VORT EOF1 SHEAR EOF1 2.0 MSE EOF2 1.5 1.0 0.5 0.0 -0.5 -1.0 -1.5 0.58 -2.0 0.72 0.67 -2.5 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 16

Wavelet Analysis of Intense Typhoon Occurrence Frequency Wavelet Analysis of Intense Typhoon Occurrence Frequency 2-7 yr 16-32 yr Period A1 Period B Period A2 Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 17

Period A1 Period A2 Period B Ocean Ocean Temperature Temperature Anomalies Anomalies Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 18

Vertical Wind Shear Vertical Wind Shear Period A1 minus Period B Period A2 minus Period B Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 19

Period A1 Period A2 Period B Frequency of Frequency of Occurrence of Intense Occurrence of Intense Typhoons Typhoons Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 20

Difference in the Frequency of Occurrence of Intense Typhoons Difference in the Frequency of Occurrence of Intense Typhoons Proceedings, Royal Society A (2008) Proceedings, Royal Society A (2008) Period A1 minus Period B Period A2 minus Period B Blue shading: 95% Green shading: 90% Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 21