Water balance of the Mekong river basin during GAME IOP

Kooiti MASUDA (Frontier Research System for Global Change)

• W: atmospheric Water vapor content ("precipitatble water")
• S: terrestrial water Storage (surface water + soil moisture + groundwater)

• C: water vapor Convergence
• P: Precipitation
• E: Evaporation
• R: Runoff

• GAME: GEWEX Asian Monsoon Experiment
• GEWEX: Global Energy and Water Cycle Experiment
• IOP: Intensive Observation Period

Values from

• Dai, A. and Trenberth, K.E. (2002) J. Hydrometeorology, 3, 660 - 687.

1	Amazon	6642
2	Congo	1308
3	Orinoco	1129
4	Changjiang	944
5	Brahmaputra	628
6	Mississippi	610
7	Yenisey	599
8	Parana	568
9	Lena	531
10	Mekong	525
11	Tocantins	511
12	Tapajos	415	Tributary of Amazon, but measured separately
13	Ob	412
14	Ganges	404
15	Irrawaddy	393

• R -- runoff -- River discharge ... daily
  • Mekong River Commission, Lower Mekong Hydrologic Yearbook 1998

• C -- moisture convergence; W -- moisture content
  • GAME Reanalysis 1.5 '2dmon' (12-18 hour forecasts) ... 6-hourly, Apr.-Oct.

• P -- precipitation
  • Station rain gauges ... explained later
  • Global Precip. Climatology Centre, "Monitoring Product" (gauges) monthly
  • Global Precip. Climatology Project, "1-degree daily" product (satel.+gauges)
  • GAME Reanalysis 1.5 (forecasts) ... 6-hourly, Apr.-Oct.

• E -- evaporation
  • Residuals from above P, C and dW/dt
  • GAME Reanalysis 1.5 (forecasts) ... 6-hourly, Apr.-Oct.

• Template of river basin (1-deg. lat./lon.)
  • Total Runoff Integrated Pathways (Oki and Sud, 1998), modified

• Data sources
  • MRC Yearbook (Cambodia, Laos, Thailand, Viet Nam) ...daily(monthly)
  • GAME-T 'routine' (Cambodia, Laos, Myanmar, Thailand)... daily
  • GAME-T 'routine' (Viet Nam) ... 3-hourly Apr.-Sep.
  • China, National Meteorolgical Center, monthly databook ... monthly(daily)
  • HUBEX (GAME Standard Data CD-ROM) (China) ... daily May-Aug.
  • Global Historical Climatology Network (US NCDC) (India) ... monthly

• Checking for duplications and obviously erroneous records
  • Cambodia, Laos: GAME-T and MRC similar, tentatively prefer MRC
  • Viet Nam: GAME-T and MRC do not match, tentatively prefer MRC
    • Note added in Dec. 2002: MRC records are found to be wrong here.
  • Thailand: duplications between GAME-T and MRC still remain
  • China: HUBEX data miss some days of obs., prefer NMC databook.

• Calculation of monthly sums

• Interpolation into 1-degree latitude-longitude grid
  • Smooth surface fitting with "surface" of "Generic Mapping Tools"

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