Seasonal Climate CyclesSeasonal Climate Cycles

Sea level pressure

Sea Level PressureSea Level Pressure

• Pressure is a measure of the atmosphere’s weight

• Lows associated with colder temperatures

• Highs associated with warmer temperatures

SEASONAL CYCLE OF PRESSURE - SEASONAL CYCLE OF PRESSURE - NORTHERN HEMISPHERENORTHERN HEMISPHERE

LOOK FOR THE FOLLOWNG:

WINTER (OCEANS WARMER THAN LAND)

• DOMINANCE OF LOWS OVER NORTHERN OCEANS• HIGH PRESSURE OVER COMPARATIVELY COLD LAND

SUMMER (LAND WARMER THAN OCEANS)

• DOMINANCE OF HIGHS OVER NORTHERN OCEANS• LOW PRESSURE OVER RELATIVELY WARM LAND

OTHER

• TREMENDOUS WINTER/SUMMER PRESSURE CHANGE OVER ASIA (PART OF THE ASIAN MONSOON)

• GENERAL LOW PRESSURE REGION NEAR THE EQUATOR

MAXIMUM DEVELOPMENT OF: ALEUTIAN AND ICELANDIC LOWS SIBERIAN AND BERMUDA HIGHS

JAN

FEB

SIBERIAN HIGH INTENSEOTHER HIGHS AND LOWS WEAKEN

MAR

ALEUTIAN AND ICELANDIC LANDS WEAKENPACIFIC AND BERMUDA HIGHS EXPAND AND STRENGTHEN

APR

LOWS CONTINUE TO WEAKEN, HIGHS TO STRENGTHEN

MAY

HIGHS DOMINANT OVER OCEAN, LOWS OVER LAND

JUN

LOWS EXPANDS OVER LAND, ESPECIALLY ASIA

JUL

MAXIMUM DEVELOPMENT OF 1) PACIFIC AND BERMUDA HIGHS 2) LOW PRESSURE OVER LAND (ESPECIALLY ASIA)

AUG

HIGHS BEGIN TO WEAKEN

SEP

HIGHS CONTINUE TO WEAKENLOWS BEGIN TO WEAKEN OVER NORTHERN OCEANS

OCT

HIGH PRESSURE WEAKENS OVER OCEANSHIGH PRESSURE STARTS TO DEVELOP OVER LANDLOW PRESURE DEVELOPS OVER NORTHERN OCEANS

NOV

LOW PRESSURE EXPANDS OVER NORTHERN OCEANSHIGH PRESURE EXPANDS OVER LAND

DEC

EXTREME AREA OF HIGH PRESSURE OVER ASIA(CENTERED ON SIBERIA, CALLED SIBERIAN HIGH)

SEASONAL CYCLE OF PRESSURE - SEASONAL CYCLE OF PRESSURE - SOUTHERN HEMISPHERESOUTHERN HEMISPHERE

LOOK FOR THE FOLLOWNG• HIGH PRESSURE OVER OCEANS ALL YEAR• CONTINUOUS BAND OF HIGH PRESSURE IN WINTER• HIGH PRESSURE CELLS OVER OCEANS IN SUMMER• LOW PRESSURE OVER LAND IN SUMMER• LESS SEASONAL CHANGE THAN IN NORTHERN HEMI.• HIGH PRESSURE MOST DEVELOPED IN JULY & AUGUST• LOW PRESSURE MOST DEVELOPED DEC TO FEB

HIGH PRESSURE OVER OCEANS ALL YEARCONTINUOUS BAND OF HIGH PRESSURE IN WINTERHIGH PRESSURE CELLS OVER OCEANS IN SUMMERLOW PRESSURE OVER LAND IN SUMMERLESS SEASONAL CHANGE THAN IN NORTHERN HEM.HIGH PRESSURE MOST DEVELOPED IN JULY & AUGLOW PRESSURE MOST DEVELOPED DEC TO FEB

HIGH PRESSURE OVER OCEANS ALL YEARCONTINUOUS BAND OF HIGH PRESSURE IN WINTERHIGH PRESSURE CELLS OVER OCEANS IN SUMMERLOW PRESSURE OVER LAND IN SUMMERLESS SEASONAL CHANGE THAN IN NORTHERN HEM.HIGH PRESSURE MOST DEVELOPED IN JULY & AUGLOW PRESSURE MOST DEVELOPED DEC TO FEB

HIGH PRESSURE OVER OCEANS ALL YEARCONTINUOUS BAND OF HIGH PRESSURE IN WINTERHIGH PRESSURE CELLS OVER OCEANS IN SUMMERLOW PRESSURE OVER LAND IN SUMMERLESS SEASONAL CHANGE THAN IN NORTHERN HEM.HIGH PRESSURE MOST DEVELOPED IN JULY & AUGLOW PRESSURE MOST DEVELOPED DEC TO FEB

HIGH PRESSURE OVER OCEANS ALL YEARCONTINUOUS BAND OF HIGH PRESSURE IN WINTERHIGH PRESSURE CELLS OVER OCEANS IN SUMMERLOW PRESSURE OVER LAND IN SUMMERLESS SEASONAL CHANGE THAN IN NORTHERN HEM.HIGH PRESSURE MOST DEVELOPED IN JULY & AUGLOW PRESSURE MOST DEVELOPED DEC TO FEB

HIGH PRESSURE OVER OCEANS ALL YEARCONTINUOUS BAND OF HIGH PRESSURE IN WINTERHIGH PRESSURE CELLS OVER OCEANS IN SUMMERLOW PRESSURE OVER LAND IN SUMMERLESS SEASONAL CHANGE THAN IN NORTH. HEM.HIGH PRESSURE MOST DEVELOPED IN JULY & AUGLOW PRESSURE MOST DEVELOPED DEC TO FEB

HIGH PRESSURE OVER OCEANS ALL YEARCONTINUOUS BAND OF HIGH PRESSURE IN WINTERHIGH PRESSURE CELLS OVER OCEANS IN SUMMERLOW PRESSURE OVER LAND IN SUMMERLESS SEASONAL CHANGE THAN IN NORTHERN HEM.HIGH PRES. MOST DEVELOPED IN JULY & AUGLOW PRESSURE MOST DEVELOPED DEC TO FEB

HIGH PRESSURE OVER OCEANS ALL YEARCONTINUOUS BAND OF HIGH PRESSURE IN WINTERHIGH PRESSURE CELLS OVER OCEANS IN SUMMERLOW PRESSURE OVER LAND IN SUMMERLESS SEASONAL CHANGE THAN IN NORTHERN HEM.HIGH PRESSURE MOST DEVELOPED IN JULY & AUGLOW PRESSURE MOST DEVELOPED DEC TO FEB