The Tropospheric Seasonally Varying Mean Climate over the Western Hemisphere (1979-1995)

Figure 1. Zonal mean (0 - 180 °W) January pressure-latitude cross section of temperature and meridional temperature gradient (top panel, heavy solid lines and thin lines, respectively), and zonal wind and combined vertical motion and meridional component of the divergent wind (bottom panel, solid lines and vectors, respectively) for 1979-1995. Contour intervals are 10 K and 0.1 K lat-1, respectively (top), and 5 m s-1 (bottom). The characteristic vector indicates a divergent wind of 5 m s-1 or pressure vertical velocity of 50 hPa d-1. Light (dark) shading indicates values less (greater) than 0.5 (0.5) K lat-1 (top). Zonal wind speeds greater than 15 (30) m s-1 are indicated by light (dark) shading (bottom).

Figure 2. Same as Fig. 1, except for July.

Figure 3. Time-longitude section at 35 °N of the mean (1979-1995) zonal 700-200 hPa thickness gradient (top) and meridional wind (bottom). Contour interval is 1 x 10 5 (top) and 2 m s-1 (bottom).

Figure 4. Same as Fig. 3, except for 25 °S.

Figure 5. Mean (1979-1995) January analyses of sea level pressure (top left), 925-hPa stream lines and isotachs (top right), precipitable water (bottom left) and precipitation (bottom right) for the Western Hemisphere. Contour intervals are 4 hPa for sea level pressure, 5 m s-1 for 925-hPa wind speed, 5 mm for precipitable water and 50 mm for precipitation. Light (dark) shading indicates wind speeds greater than 5 (10) m s-1 (top right), precipitable water greater than 30 (45) mm (bottom left), and precipitation greater than 100 (200) mm (bottom right).

Figure 6. Same as Fig. 5, except for February.

Figure 7. Same as Fig. 5, except for March.

Figure 8. Same as Fig. 5, except for April.

Figure 9. Same as Fig. 5, except for May.

Figure 10. Same as Fig. 5, except for June.

Figure 11. Same as Fig. 5, except for July.

Figure 12. Same as Fig. 5, except for August.

Figure 13. Same as Fig. 5, except for September.

Figure 14. Same as Fig. 5, except for October.

Figure 15. Same as Fig. 5, except for November.

Figure 16. Same as Fig. 5, except for December.

Figure 17. Same as Fig. 5, except for December-February. Precipitation is average monthly total.

Figure 18. Same as Fig. 5, except for March-May. Precipitation is average monthly total.

Figure 19. Same as Fig. 5, except for June-August. Precipitation is average monthly total.

Figure 20. Same as Fig. 5, except for September-November. Precipitation is average monthly total.

Figure 21. Mean (1979-1995) January analyses of outgoing longwave radiation (top left), 500-hPa pressure vertical velocity (top right), 200-hPa stream lines and isotachs (bottom left), and 200-hPa velocity potential and divergent wind (bottom right) for the Western Hemisphere. Contour intervals are 10 W m-2 for OLR, 20 hPa d-1 for pressure vertical velocity, 10 m s-1 for wind speed, and 1 x 106 m2 s-1 for velocity potential. The sample vector represents a divergent wind speed of 5 m s-1. Light (dark) shading indicates OLR less than 240 (200) W m-2, pressure vertical velocity less (greater) than -20 (20) hPa d-1, and wind speed greater than 30 (50) m s-1.

Figure 22. Same as Fig. 21, except for February.

Figure 23. Same as Fig. 21, except for March.

Figure 24. Same as Fig. 21, except for April.

Figure 25. Same as Fig. 21, except for May.

Figure 26. Same as Fig. 21, except for June.

Figure 27. Same as Fig. 21, except for July.

Figure 28. Same as Fig. 21, except for August.

Figure 29. Same as Fig. 21, except for September.

Figure 30. Same as Fig. 21, except for October.

Figure 31. Same as Fig. 21, except for November.

Figure 32. Same as Fig. 21, except for December.

Figure 33. Same as Fig. 21, except for December-February.

Figure 34. Same as Fig. 21, except for March-May.

Figure 35. Same as Fig. 21, except for June-August.

Figure 36. Same as Fig. 21, except for September-November.

Figure 37. Mean (1979-1995) January analyses of sea level pressure (top left), 925-hPa stream lines and isotachs (top right), precipitable water (bottom left) and precipitation (bottom right) over the South American region. Contour intervals are 4 hPa for sea level pressure, 5 m s-1 for 925-hPa wind speed, 5 mm for precipitable water and 50 mm for precipitation. Light (dark) shading indicates wind speeds greater than 5 (10) m s-1 (top right), precipitable water greater than 30 (45) mm (bottom left), and precipitation greater than 100 (200) mm (bottom right).

Figure 38. Same as Fig. 37, except for February.

Figure 39. Same as Fig. 37, except for March.

Figure 40. Same as Fig. 37, except for April.

Figure 41. Same as Fig. 37, except for May.

Figure 42. Same as Fig. 37, except for June.

Figure 43. Same as Fig. 37, except for July.

Figure 44. Same as Fig. 37, except for August.

Figure 45. Same as Fig. 37, except for September.

Figure 46. Same as Fig. 37, except for October.

Figure 47. Same as Fig. 37, except for November.

Figure 48. Same as Fig. 37, except for December.

Figure 49. Same as Fig. 37, except for December-February. Precipitation is average monthly total.

Figure 50. Same as Fig. 37, except for March-May. Precipitation is average monthly total.

Figure 51. Same as Fig. 37, except for June-August. Precipitation is average monthly total.

Figure 52. Same as Fig. 37, except for September-November. Precipitation is average monthly total.

Figure 53. Mean (1979-1995) January analyses of outgoing longwave radiation (top left), 500-hPa pressure vertical velocity (top right), 200-hPa stream lines and isotachs (bottom left), and 200-hPa velocity potential and divergent wind (bottom right) over the South American region. Contour intervals are 10 W m-2 for OLR, 20 hPa d-1 for pressure vertical velocity, 10 m s-1 for wind speed, and 1 x 106 m2 s-1 for velocity potential. The sample vector represents a divergent wind speed of 5 m s-1. Light (dark) shading indicates OLR less than 240 (200) W m-2, pressure vertical velocity less (greater) than -20 (20) hPa d-1, and wind speed greater than 30 (50) m s-1.

Figure 54. Same as Fig. 53, except for February.

Figure 55. Same as Fig. 53, except for March.

Figure 56. Same as Fig. 53, except for April.

Figure 57. Same as Fig. 53, except for May.

Figure 58. Same as Fig. 53, except for June.

Figure 59. Same as Fig. 53, except for July.

Figure 60. Same as Fig. 53, except for August.

Figure 61. Same as Fig. 53, except for September.

Figure 62. Same as Fig. 53, except for October.

Figure 63. Same as Fig. 53, except for November.

Figure 64. Same as Fig. 53, except for December.

Figure 65. Same as Fig. 53, except for December-February.

Figure 66. Same as Fig. 53, except for March-May.

Figure 67. Same as Fig. 53, except for June-August.

Figure 68. Same as Fig. 53, except for September-November.

Figure 69. Mean (1979-1995) January analyses of sea level pressure (top left), 925-hPa stream lines and isotachs (top right), precipitable water (bottom left) and precipitation (bottom right) for the region of the United States, Central America and northwest South America. Contour intervals are 4 hPa for sea level pressure, 5 m s-1 for 925-hPa wind speed, 5 mm for precipitable water and 50 mm for precipitation. Light (dark) shading indicates wind speeds greater than 5 (10) m s-1 (top right), precipitable water greater than 30 (45) mm (bottom left), and precipitation greater than 100 (200) mm (bottom right).

Figure 70. Same as Fig. 69, except for February.

Figure 71. Same as Fig. 69, except for March.

Figure 72. Same as Fig. 69, except for April.

Figure 73. Same as Fig. 69, except for May.

Figure 74. Same as Fig. 69, except for June.

Figure 75. Same as Fig. 69, except for July.

Figure 76. Same as Fig. 69, except for August.

Figure 77. Same as Fig. 69, except for September.

Figure 78. Same as Fig. 69, except for October.

Figure 79. Same as Fig. 69, except for November.

Figure 80. Same as Fig. 69, except for December.

Figure 81. Same as Fig. 69, except for December-February. Precipitation is average monthly total.

Figure 82. Same as Fig. 69, except for March-May. Precipitation is average monthly total.

Figure 83. Same as Fig. 69, except for June-August. Precipitation is average monthly total.

Figure 84. Same as Fig. 69, except for September-November. Precipitation is average monthly total.

Figure 85. Mean (1979-1995) January analyses of outgoing longwave radiation (top left), 500-hPa pressure vertical velocity (top right), 200-hPa stream lines and isotachs (bottom left), and 200-hPa velocity potential and divergent wind (bottom right) for the region of the United States, Central America and northwest South America. Contour intervals are 10 W m-2 for OLR, 20 hPa d-1 for pressure vertical velocity, 10 m s-1 for wind speed, and 1 x 106 m2 s-1 for velocity potential. The sample vector represents a divergent wind speed of 5 m s-1. Light (dark) shading indicates OLR less than 240 (200) W m-2, pressure vertical velocity less (greater) than -20 (20) hPa d-1, and wind speed greater than 30 (50) m s -1.

Figure 86. Same as Fig. 85, except for February.

Figure 87. Same as Fig. 85, except for March.

Figure 88. Same as Fig. 85, except for April.

Figure 89. Same as Fig. 85, except for May.

Figure 90. Same as Fig. 85, except for June.

Figure 91. Same as Fig. 85, except for July.

Figure 92. Same as Fig. 85, except for August.

Figure 93. Same as Fig. 85, except for September.

Figure 94. Same as Fig. 85, except for October.

Figure 95. Same as Fig. 85, except for November.

Figure 96. Same as Fig. 85, except for December.

Figure 97. Same as Fig. 85, except for December-February.

Figure 98. Same as Fig. 85, except for March-May.

Figure 99. Same as Fig. 85, except for June-August.

Figur 100. Same as Fig. 85, except for September-November.

Figur 101. Evolution of the South American monsoon system (upper troposphere - Bolivian high). Time-longitude section of monthly mean (1979-1995) 200-hPa geopotential height at 15 °S. Contour interval is 10 m. Light (dark) shading indicates values less (greater) than 12370 (12430) m.

Figure 102. Evolution of the South American monsoon system (lower troposphere). Time-longitude section of monthly mean (1979-1995) 850-hPa geopotential height at 15 °S. Contour interval is 5 m. Light (dark) shading indicates values less (greater) than 1510 (1530) m.

Figure 103. Pressure-longitude section of seasonal mean (1979-1995) relative humidity (contours and shading), and combined pressure vertical velocity and zonal divergent wind (vectors) at 15 °S, for December-February (top) and March-May (bottom). Contour interval is 10%. Light (dark) shading indicates values greater than 50 (70) %. The vertical velocity and zonal divergent wind have been scaled for display. Regions of elevated terrain have been masked out. Relative humidity is not available in the reanalysis archive for pressure less than 300 hPa.

Figure 104. Same as Fig. 103, except for June-August (top) and September-November (bottom).

Figure 105. Pressure-latitude section of seasonal mean (1979-1995) relative humidity (thin contours and shading), zonal wind speed (thick contours), and combined pressure vertical velocity and meridional divergent wind (vectors) at 30 °W, for December-February (top) and March-May (bottom). Contour interval for RH (zonal wind speed) is 10% (5 m s-1). Light (dark) shading indicates RH values greater than 50 (70) %. The vertical velocity and zonal divergent wind have been scaled for display.

Figure 106. Same as Fig. 105, except for June-August (top) and September-November (bottom).

Figure 107. Same as Fig. 105, except at 60 °W.

Figure 108. Same as Fig. 105, except at 60 °W and for June-August (top) and September-November (bottom).

Figure 109. Same as Fig. 105, except at 90 °W.

Figure 110. Same as Fig. 105, except at 90 °W and for June-August (top) and September-November (bottom).

Figure 111. Same as Fig. 105, except at 120 °W.

Figure 112. Same as Fig. 105, except at 120 °W and for June-August (top) and September-November (bottom).

Figure 113. Time-latitude section of monthly mean (1979-1995) 500-hPa pressure vertical velocity (hPa d-1) at 30 °W. Contour interval is 10 hPa d-1. Light (dark) shading indicates values less than 20 ( 40) hPa d-1.

Figure 114. Time-latitude section of monthly mean (1979-1995) precipitation intensity (mm d-1) at 30 °W. Contour interval is 2 mm d-1. Light (dark) shading indicates values greater than 4 (8) mm d-1. Data source is the NCEP/NCAR Reanalysis archive.

Figure 115. Time-latitude section of monthly mean (1979-1995) precipitation intensity (mm d-1) at 30 °W. Contour interval is 2 mm d-1. Light (dark) shading indicates values greater than 4 (8) mm d-1. Data source is the archive of merged satellite estimates and rain gauge observations (Xie and Arkin 1996).

Figure 116. Time-latitude section of monthly mean (1979-1995) outgoing longwave radiation (W m-2) at 30 °W. Contour interval is 10 W m-2. Light (dark) shading indicates values less than 240 (210) W m-2.

Figure 117. Same as Fig. 113, except at 60 °W.

Figure 118. Same as Fig. 114, except at 60 °W.

Figure 119. Same as Fig. 115, except at 60 °W.

Figure 120. Same as Fig. 116, except at 60 °W.

Figure 121. Same as Fig. 113, except at 90 °W.

Figure 122. Same as Fig. 114, except at 90 °W.

Figure 123. Same as Fig. 115, except at 90 °W.

Figure 124. Same as Fig. 116, except at 90 °W.

Figure 125. Same as Fig. 113, except at 120 °W.

Figure 126. Same as Fig. 114, except at 120 °W.

Figure 127. Same as Fig. 115, except at 120 °W.

Figure 128. Same as Fig. 116, except at 120 °W.