Monteverde : Ecology and Conservation of a Tropical Cloud Forest

Figure 2.4. Hourly mean instantaneous shortwave
radiation (W/m^2 ) calculated for clear-sky conditions
during 21 April p) and 21 December (•), and measured
hourly mean instantaneous shortwave radiation at a
leeward cloud forest site in the MCFP during days with
convective precipitation (•), wind-driven precipitation
(•), and mist and cloud (4). Values for precipitation,
mist, and cloud are means of three days each measured
during October 1991 to September 1992. See text for a
definition of precipitation types.

2.1.2. Temperature

The reduction in ambient air temperature with in-
creasing altitude (adiabatic cooling) causes air tem-
peratures to be lower at Monteverde compared to low-
land sites but higher than at montane sites in Costa
Rica such as Villa Mills (3000 m) and Volcan Irazu
(3400 m; Table 2.1, Fig. 2.5). Mean annual tempera-

ture at Monteverde measured at 1460 m from 1956

to 1995 was 18.5°C, with a minimum of 9.0°C and a

maximum of 27.0°C (J. Campbell, unpubl. data). Mean

monthly minimum and maximum temperatures dur-

ing the same period had ranges of 14.0-17.6°C in De-

cember and 16.5-21.2°C in June, respectively (Fig.

2.5). The coolest air temperatures are associated with

outbreaks of polar air, which typically originate in

North America (see Sec. 2.1.4). Air temperatures at

lower elevations on the Caribbean and Pacific slopes

of the Monteverde area are higher, but no long-term

records exist.

2.1.3. Cloud Water and Precipitation

Mean annual precipitation depth measured at 1460

m at Monteverde from 1956 to 1995 was 2519 mm.

Minimum and maximum annual precipitation during

that time were 1715 mm (1959) and 3240 mm (1996),

respectively (J. Campbell, unpubl. data; Table 2.1, Fig.

2.6). Reported precipitation depths are minimum es-

timates for the upper portions of Monteverde because

standard rain gauges substantially underestimate wind-

driven cloud water and precipitation. For example,

at a leeward cloud forest site (20 m higher in eleva-

tion and ca. 2.5 km east-southeast from the Monte-

verde weather station), annual precipitation depth

collected in 1991-92 with a standard rain gauge was

3191 mm; an additional 886 mm of wind-driven cloud

water and precipitation was collected with a cloud

water collector (Clark 1994). Additional wind-driven

inputs represented 22% of total hydrologic inputs.

In comparison, reported precipitation depth for the

Monteverde weather station was 2223 mm for this

period.

Precipitation throughout the Cordillera varies spa-

tially with elevation and exposure to the tradewinds.

Table 2.1. Longitude, latitude, elevation in meters, mean annual temperature (in °C), and mean annual
precipitation (in mm) for selected locations in Costa Rica.

Location

Limon
Villa Mills
Volcan Irazu
La Selva
San Jose
Ciudad Quesada
Monteverde
Cano Negro
Puntarenas
Nicoya

Longitude

83°02'

83°32'

83°51'

83°58'

84°04'

84°25'

84°46'

84°49'

84°50'

85°27'

Latitude

10°00'

9°30'

9°59'

10°26'

9°56'

10°20'

10°15f

10°24'

9°58'

10°09'

Elevation

(m)

3

3000

3400

25

1172

656

1460

720

4

123

Mean Annual

Temperature

(°C)

25.3

10.9

7.9

25.8

20.0

22.6

18.8

H

27.1

26.5

Mean Annual

Precipitation

(mm)

3531

2679

2025

3962

1902

4543

2519

4484

1564

H

Source: Data are taken from Herrera (1985), Vargas (1994), and J. Campbell (unpubl. data).
(-) = data unavailable.

17 The Physical Environment