- #1
Fisic
- 9
- 6
Please correct me if I'm well off the fairway with the following theory.
We all know that atmospheric conditions (temperature, pressure, dewpoint, etc.) can affect many different bodies in motion, from aeroplanes to cars to golf balls. But in the case of a golf ball, exactly how big is the effect? How much more club do you need in the winter versus the summer?
Let's assume wind is calm and we're playing a golf course at sea level. Round 1 is played on a dull winter morning, temperature 0 °C, relative humidity 80%, while Round 2 is on a sunny afternoon in mid-July, temperature 28 °C, relative humidity 70%. Assume in both cases atmospheric pressure is the standard 1013 hPa.
The only differences in conditions are therefore the air temperature, specific humidity (as measured by dewpoint) and ground temperature (which greatly affects the temperature of the ball and hence the compressibility of its elastomeric core). In summer, the grassy surface can get several degrees warmer than the overlying air, so assume it's 35 °C in this case. In winter, assume it's the same as the air (or else there would be ground frost and the course would be closed).
The density of the air is the primary factor affecting the aerodynamic performance of the golf ball and is calculated for both scenarios below (using the Density Altitude tool in the Aviation Pocketknife app). The density of 1.290 kg/m³ in winter is 11.2% higher than in summer (1.160 kg/m³).
The drag force (air-resistance), FD, felt by the ball is given by the expression
FD = ½ρCDAν2
where CD is the Coefficient of Drag of the ball and A its area facing the air, both the same in the two scenarios and therefore constant, and ν is its speed. The only difference is therefore the air density, ρ. In summer, the drag force is 11.2% lower than in winter, therefore the ball will travel that much further, all other things being equal. If you get 140 yards from your 9-iron in the winter scenario you're talking around 155 yards in summer (i.e about a 1-club difference). A 250-yard winter carry becomes near 280 yards in summer (and the numbers get crazy for DeChambeau and Bubba...)
In reality, all other things are not equal and other factors are at play, primarily the ground (ball) temperature. As the golf ball is lying on the ground for the vast majority of the time, the temperature of its elastomeric core will adjust towards the ground temperature during the round. I read somewhere that the ideal core temperature is 27 °C (though I'm sure it varies for different balls brands), therefore in the winter scenario we can expect the core to cool down towards 0 °C as the round progresses. This will reduce the compression and spring off the clubface and therefore take distance off the shot, but exactly how much I'm not sure. Anyone? I always store my golf balls indoors overnight before I play winter golf here in Ireland and keep a spare ball in each pocket, switching balls between holes. It does keep the balls warmer than if they were in my bag and I do see and feel a difference, but I'm just not a good enough golfer to be able to quantify this accurately.
In summer, the core is closer to the optimum temperature and therefore distance is maximised. Also, the ground will most likely be harder, adding more rollout to the shot. I said above that the only difference in the drag equation is the air density, however the launch speed of the ball will probably differ too, being faster with the warmer core in the summer.
Overall, we have around 11% lower air-resistance, a faster ball speed and longer roll in summer. The optimum conditions are on a warm, humid day with low atmospheric pressure, while the worst are on a cold, dry day in a winter anticyclone. If the winter and summer pressures are changed to 1030 and 990 hPa, respectively, the air densities and therefore drag forces change by even more, by around 15.6%. That's 15 extra yards for every 100, or 45 yards on a 300-yard drive. No wonder these guys regularly hit it 330+ on the PGA Tour.
If anyone has any more detailed info on the important factor of ball temperature and its effect on impact dynamics I would love to hear it.
We all know that atmospheric conditions (temperature, pressure, dewpoint, etc.) can affect many different bodies in motion, from aeroplanes to cars to golf balls. But in the case of a golf ball, exactly how big is the effect? How much more club do you need in the winter versus the summer?
Let's assume wind is calm and we're playing a golf course at sea level. Round 1 is played on a dull winter morning, temperature 0 °C, relative humidity 80%, while Round 2 is on a sunny afternoon in mid-July, temperature 28 °C, relative humidity 70%. Assume in both cases atmospheric pressure is the standard 1013 hPa.
The only differences in conditions are therefore the air temperature, specific humidity (as measured by dewpoint) and ground temperature (which greatly affects the temperature of the ball and hence the compressibility of its elastomeric core). In summer, the grassy surface can get several degrees warmer than the overlying air, so assume it's 35 °C in this case. In winter, assume it's the same as the air (or else there would be ground frost and the course would be closed).
The density of the air is the primary factor affecting the aerodynamic performance of the golf ball and is calculated for both scenarios below (using the Density Altitude tool in the Aviation Pocketknife app). The density of 1.290 kg/m³ in winter is 11.2% higher than in summer (1.160 kg/m³).
| Air | Relative humidity | Dewpoint | Air density [kg/m³] | Ground temperature | |
| Round 1 | 0 °C | 80% | -3 °C | 1.290 | 0 °C |
| Round 2 | 28 °C | 70% | 22 °C | 1.160 | 35 °C |
The drag force (air-resistance), FD, felt by the ball is given by the expression
FD = ½ρCDAν2
where CD is the Coefficient of Drag of the ball and A its area facing the air, both the same in the two scenarios and therefore constant, and ν is its speed. The only difference is therefore the air density, ρ. In summer, the drag force is 11.2% lower than in winter, therefore the ball will travel that much further, all other things being equal. If you get 140 yards from your 9-iron in the winter scenario you're talking around 155 yards in summer (i.e about a 1-club difference). A 250-yard winter carry becomes near 280 yards in summer (and the numbers get crazy for DeChambeau and Bubba...)
In reality, all other things are not equal and other factors are at play, primarily the ground (ball) temperature. As the golf ball is lying on the ground for the vast majority of the time, the temperature of its elastomeric core will adjust towards the ground temperature during the round. I read somewhere that the ideal core temperature is 27 °C (though I'm sure it varies for different balls brands), therefore in the winter scenario we can expect the core to cool down towards 0 °C as the round progresses. This will reduce the compression and spring off the clubface and therefore take distance off the shot, but exactly how much I'm not sure. Anyone? I always store my golf balls indoors overnight before I play winter golf here in Ireland and keep a spare ball in each pocket, switching balls between holes. It does keep the balls warmer than if they were in my bag and I do see and feel a difference, but I'm just not a good enough golfer to be able to quantify this accurately.
In summer, the core is closer to the optimum temperature and therefore distance is maximised. Also, the ground will most likely be harder, adding more rollout to the shot. I said above that the only difference in the drag equation is the air density, however the launch speed of the ball will probably differ too, being faster with the warmer core in the summer.
Overall, we have around 11% lower air-resistance, a faster ball speed and longer roll in summer. The optimum conditions are on a warm, humid day with low atmospheric pressure, while the worst are on a cold, dry day in a winter anticyclone. If the winter and summer pressures are changed to 1030 and 990 hPa, respectively, the air densities and therefore drag forces change by even more, by around 15.6%. That's 15 extra yards for every 100, or 45 yards on a 300-yard drive. No wonder these guys regularly hit it 330+ on the PGA Tour.
If anyone has any more detailed info on the important factor of ball temperature and its effect on impact dynamics I would love to hear it.