Snow lysimeter runoff

The chart above shows the hourly runoff pattern from the snow lysimeters in the mature cedar and larch locations during mid-January to the end of February. There are many similarities, but also some interesting differences between the forest sites. All of the large peaks are associated with rain-on-snow events and these give similar runoff amounts for both locations.

The largest event starting on 11 February brought strong winds and rainfall of up to 4.5 mm/h, although temperatures remained only just above freezing point in the forest (larch site: 0.6 C, cedar site 0.2 C). With these cool temperatures we might assume the precipitation was snowfall, but the lysimeter runoff response shows a large peak that could only occur with rainfall. The local Murakami weather station nearer the coast shows a warm front moved in and temperatures rose to over 5 degrees Celsius.

In early February there are several small peaks at the cedar site which are not recorded at the larch site. This is most likely due to melting of intercepted snow in the cedar canopy.

The last two weeks of February show elevated levels of runoff (even night-time melting) due to rising temperatures and higher amounts of radiation in the energy balance. In this period we can see the runoff from the larch site generally exceeds that in the cedar site, where there is greater shading of the snowpack.