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Physical Monitoring Program |
Equipment Descriptions |
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| Rainfall Rainfall is collected in the Clearing by two US Forestry Specifications No 5100-4515A rain gauges , and by a Hydrological Services tipping bucket rain gauge. The rain gauges are read at approximately 9:00 am every day - except weekends and holidays. The tipping bucket records precipitation on 5-minute intervals. While the tipping bucket provides a continuous record of rainfall, they tend to underestimate total rainfall by as much as 10%. For that reason are not used to provide data on absolute rainfall totals. Each tipping bucket event represents 0.254 mm (0.01") of rainfall. A computer program was written that uses tipping bucket rainfall data to estimate rain gauge data for those days when readings are not made. For example, the program takes the total rainfall recorded on Monday mornings and divides it up proportionally according to the rainfall recorded by the tipping bucket from Friday 9:00am to Monday 8:59am. The estimated rainfall for the missed days is exactly equal to the rainfall collected by the rain gauge. |
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Seasonality (wet vs. dry seasons) The beginning and end dates of the Panama Canal watershed dry season are determined by the Meteorological and Hydrological Branch of the Panama Canal Authority. The PCA defines the transition between seasons by tracking 11 variables (see list below). The are no publications justifying the use of this system and any questions should be directed to Jorge Espinosa (JESPINO@SINFO.NET) of the Meteorological & Hydrological Branch of the ACP.Westerly Component of 300 HPA Wind Gatun Lake Basin evaporation > 0.13" day-1 Sea temperature at Amador < 80 °F < 5 grams of water vapor kg-1 below 12,00 ft Temp-Dew point difference SFC-400 HPA., > 10°CHoward Air force Base wind speed SFC-4000 ft., > 15 knots Inter-Tropical Convergence Zone > 2 deg. Lat. south of Panama Pacific Coast sea breeze < 2 hours day-1 Atlantic Coast surface wind average > 6.0 M.P.H. Gatun Lake level (corrected for water usage) falling Gatun Watershed daily rainfall average (of 26 stations) < .25" |
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| Run-off at the Lutz catchment area is determined from the water level in a 120° V-notch weir. The height of the water is recorded by two separate instruments: continuously by a Stevens A-71 strip-chart water level recorder connected to a float in a stilling well, and at five-minute intervals with an ISCO Bubble Flow Meter. Data from these devices are converted (either directly or through a digitizing process) into run-off (m3) and then into rainfall equivalents | |
| Soil moisture are determined gravimetrically based on samples collected weekly (Dec. to May) and every two weeks (Jun. to Nov.). Samples are taken at two depths (0-10cm and 30-40cm) from ten sites in the Lutz catchment area. Samples of approximately 2.5 cm soil cores are made with an ‘Oakfield punch’. Samples are weighed and placed in a drying oven at 120°C for approximately 48 hrs and then re-weighed. | |
| Relative Humidity Hourly average, maximum and minimum relative humidity is measured using Bacharach Pocket-sized Sling Psychrometers and Vaisala electronic temperature/humidity sensors. Measurements in the Clearing, at the base and top of the Lutz tower (1m and 40m, respectively) are made at approximately 12:30 p.m. using the Sling Psychrometers. Data are also recorded on an hourly basis using the Vaisala sensors at 1, 10, 20, 30 and 40m on the Lutz Tower and at 1m in the Clearing. | |
| Temperature Hourly average, maximum and minimum shaded air temperature is measured in the Clearing inside a standard Instrument Shelter and at the base and the top of the Lutz Tower by Taylor max-min thermometers at approximately 9:00am. Data are also recorded on an hourly basis by data loggers attached to HMP35C & HMP45C Vaisala electronic temperature/humidity sensors. | |
| Solar Radiation Hourly total, maximum and minimum global solar radiation are measured at the top of the Lutz tower using Li-Cor LI200SB pyranometers attached to a data logger. Hourly total, maximum and minimum are recorded. Li-Cor 190SB sensors record Photosynthetically Active Radiation (PAR) similarly. | |
| Wind Speed and Direction Hourly average, maximum and minimum wind speed plus average wind direction are recorded at hourly intervals on the top of the Lutz tower using a Model 05035 Young Anemometer connected to a data logger. Total wind passage is also recorded on working days at approximately 9:30 am using an Analog Totalizing Anemometer. This device is believed to be more accurate than the Young Anemometer, especially during periods of low wind speeds (common during the rainy season) due to totalizing anemometer's lower wind-speed threshold. | |
| Estimated Evapotranspiration and Water Balance Evapotranspiration is estimated using ceramic plate atmometers known as ETgage. ETgages estimate evapotranspiration by allowing water to be drawn up through a ceramic disk and out through a Gore-Tex cover. There are three ETgages currently being used on BCI: one in the Clearing located at a height of 1.5m and two on the Lutz tower at 42 and 48m. ETgages are read at approximately the same time of day and with the same frequency and the rain gauges on BCI. The data from the ETgages are used to estimate the total water balance for the Lutz catchment. Water balance is calculated as: Rainfall - Weir run-off - Evapotranspiration. A Class A Evaporation Pan was located in the Clearing (1996 - 2002) and evaporation was recorded at the same time as the ETgage. |
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