18 Mar 2009, 9:40am
by admin

Blame sunspots for cool winter, spring weather

By George Taylor, Albany Democrat Herald, March 14, 2009 [here]

Brrrr! It’s been a cold week, in a cold month, in a cold winter. And it shows no sign of letting up.

Last week the Northwest was gripped by unseasonably cold weather. Areas west of the Cascades saw temperatures dip into the 20s. Locally we dropped as low as 27 on the 13th. Eugene was even colder (24 on the 11th). Two days later, Eugene’s 25

degree-low broke the daily record (26) set in 1944.

So far in March our local Hyslop Experiment Station has seen nine days with lows of 32 or below. The month of March averages 5.7 days, so we’re already well ahead of average for an entire March.

As cold as it was here, the Cascades generally protected us from the coldest Arctic air, which remained mostly north and east of us. On the 11th, Spokane, Wash., reported a low of 2 degrees. This was the latest date for a temperature of 2 degrees or less. The previous latest date occurred March 6, 1891. Sandpoint, Idaho, set a similar record the same day with a reading of -4 degrees, the latest date for a temperature that low.

Western Montana saw temperatures as low as -14, and subzero readings were reported in other states. In Oregon, many daily records were set, many far below the previous. Meacham was -11 on the 11th; the record for was 7, so this week’s weather broke the record by 18 degrees! LaGrande, Pendleton, Moro, The Dalles, Bend, Redmond, and others also set new records.

The cause of this cold month and cold year? Two things: the tropical Pacific and the sun.

Sea surface temperature anomalies, March 9, 2009, from the National Oceanic and Atmospheric Administration. Note the colder than average (blue) waters off the Oregon Coast. Click for larger image.

The tropical Pacific continues in its “La Nina” mode, in which ocean temperatures off South America are cooler than average. During such conditions, winters in the Northwest are cooler than average, wetter than average, or both. Snowpacks tend to be average or deeper. Thus far, we’ve had a cold but dry winter, with an average mountain snowpack.

The sun continues in its “solar minimum.” There is an 11-year cycle (about) in sunspots. When spots are plentiful, the sun’s energy is stronger, and there is a tendency for Earth’s temperatures to increase. During the low point there are few sunspots, and temperatures are more likely to drop. We have been in a solar minimum for more than a year. NASA and other agencies predicted that sunspot numbers would be increasing by now, but they are not. According to NASA, we are seeing:

* The lowest sustained solar radio flux since the F10.7 proxy was created in 1947;

* Solar wind is the lowest observed since the beginning of the space age;

* The solar wind magnetic field 36 percent weaker than during the minimum of Solar Cycle 23;

* Effectively no sunspots;

* Cosmic rays at near record-high levels.

These might make sense, but here’s what it means: The sun is quiet, and has been for an unusually long period.

Looking back over the last several hundred years, we see that solar output has been high for the last 60 years; this coincided with a general increase in temperatures. There have been some periods with low sunspot counts for many years. The early 1700s and 1800s saw lengthy solar minima, accompanied by cold temperatures.

Some solar physicists are suggesting the minimum is a harbinger of lower sunspot numbers for the next several decades. That would mean lower air temperatures, in general — global cooling!

Others suggest El Nino and La Nina conditions are driven by variations in the sun; periods with low solar output would bring La Nina conditions (such as now). We’ll see. But with a quiet sun and a continuing La Nina, I don’t expect temperatures to warm up much in the near future. Expect a cool spring, like last year.

George Taylor retired as State Climatologist last year and now operates Applied Climate Services of Corvallis.



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