Monday, September 24, 2012

How can there be frost on the golf course, it is 40° F?

How can there be frost on the golf course when it is right at 40° when I drove to the golf course this morning. First and foremost it happens and it happens a lot during the fall of the year. It is not an easy concept to understand but damage can occur to the turf if there is traffic on it when it is frosty out. Here is a very good explanation as to how it occurs.

Frost at 40 degrees! How can that be?
We had a chilly start to the day with frost in many countryside locations. Low temperatures overnight were generally in the mid 30’s to around 40.

Now let's think about this. Frost is essentially ice that forms on objects. But how can there be frost on your lawn if you check your thermometer and see temperatures above freezing? Shouldn’t it be liquid and not ice?

Yes it should be liquid, IF in fact the air temperature was really above freezing. Here’s the catch… most of our thermometers are hanging on our deck or porch wall, or if it is an indoor-outdoor thermometer, chances are the sensing bulb runs out the window. Either way, the important point is that the air temperature being measured is actually the temperature of the air a few feet above the ground and NOT right on the ground where the frost actually forms.

Often times our coldest nights are just like last night. Clear skies, light winds, the lower levels of the atmosphere are dry and the air mass is chilly. Once the sun goes down, under these conditions, the temperature drops like a rock as any heat of the day escapes back out into space. The technical term for this is “radiational cooling”.
With no heating from the sun taking place overnight, this allows colder air to settle in generally undisturbed. Since colder air is more dense (heavier) then warm air, the coldest air settles in closest to the ground, and in fact, right on the ground. If you were to take your thermometer and place it at average lawn height level (on the ground), you would likely find the temperature to be several degrees colder. If you were measuring 35 degrees several feet up you might find the lawn temperature where the coldest air settled to be 31 or 32 degrees, which is cold enough for frost to form.

So, there is nothing magical about frost forming. 32 degrees is still the freezing mark. It all comes down to WHERE is that temperature reading from. Is it several feet off the ground, were most thermometers are located, or right down on the ground?

Now you know how frost can form when your thermometer is reading in the mid 30s to around 40.

Here is another article about frost and how it can harm the turfgrass plant:

As winter starts to give way to spring-like temperatures, the desire to hit the golf course intensifies. It also signals a change in golf course management activities that can affect one's game and the conditions found on the course.

In many regions of the country, golfers occasionally face frost delays in the spring, thus pushing back starting tee times. When frost is present golf course superintendents delay play until the frost has melted. This is done to prevent damage that affects the quality of the playing surface and could potentially be very expensive to repair.

Frost is basically frozen dew that has crystallized on the grass, making it hard and brittle. A grass blade is actually 90 percent water, therefore it also freezes. Because of the short mowing height (sometimes as low as 1/8 inch) and fragile nature of the turf, putting greens are most affected by frost. Walking on frost-covered greens causes the plant to break and cell walls to rupture, thereby losing its ability to function normally. When the membrane is broken, much like an egg, it cannot be put back together.

Golfers who ignore frost delays will not see immediate damage. The proof generally comes 48-72 hours later as the plant leaves turn brown and die. The result is a thinning of the putting surface and a weakening of the plant. The greens in turn become more susceptible to disease and weeds. While it may not appear to be much of an issue if a foursome begins play early on frost-covered greens, consider the number of footprints that may occur on any given hole by one person is approximately 60. Multiply that by 18 holes with an average of 200 rounds per day and the result is 216,000 footprints on greens in a day or 6,480,000 in a month.

As golf enthusiasts superintendents do not like to delay play, but they are more concerned about turf damage and the quality if conditions for the golfer. Frost also creates a hardship on a golf facility's staff as all course preparations are put to a halt until thawing occurs. Golf carts can cause considerable damage, therefore personnel cannot maneuver around the course to mow, change cup positions, collect range balls, etc.

It may also be possible to reroute play to holes where the frost melts more quickly. But regardless of the method, the best medicine is for all to understand the hows and whys of the delay and in turn gain a greater appreciation for the golf course. It would also be wise to give the course a phone call before heading out to play to see if tee times have been pushed back due to frost.